Linux 6.14-rc3

[linux.git] / arch / x86 / kvm / xen.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright © 2019 Oracle and/or its affiliates. All rights reserved.
 * Copyright © 2020 Amazon.com, Inc. or its affiliates. All Rights Reserved.
 *
 * KVM Xen emulation
 */
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include "x86.h"
#include "xen.h"
#include "hyperv.h"
#include "irq.h"

#include <linux/eventfd.h>
#include <linux/kvm_host.h>
#include <linux/sched/stat.h>

#include <trace/events/kvm.h>
#include <xen/interface/xen.h>
#include <xen/interface/vcpu.h>
#include <xen/interface/version.h>
#include <xen/interface/event_channel.h>
#include <xen/interface/sched.h>

#include <asm/xen/cpuid.h>
#include <asm/pvclock.h>

#include "cpuid.h"
#include "trace.h"

static int kvm_xen_set_evtchn(struct kvm_xen_evtchn *xe, struct kvm *kvm);
static int kvm_xen_setattr_evtchn(struct kvm *kvm, struct kvm_xen_hvm_attr *data);
static bool kvm_xen_hcall_evtchn_send(struct kvm_vcpu *vcpu, u64 param, u64 *r);

DEFINE_STATIC_KEY_DEFERRED_FALSE(kvm_xen_enabled, HZ);

static int kvm_xen_shared_info_init(struct kvm *kvm)
{
        struct gfn_to_pfn_cache *gpc = &kvm->arch.xen.shinfo_cache;
        struct pvclock_wall_clock *wc;
        u32 *wc_sec_hi;
        u32 wc_version;
        u64 wall_nsec;
        int ret = 0;
        int idx = srcu_read_lock(&kvm->srcu);

        read_lock_irq(&gpc->lock);
        while (!kvm_gpc_check(gpc, PAGE_SIZE)) {
                read_unlock_irq(&gpc->lock);

                ret = kvm_gpc_refresh(gpc, PAGE_SIZE);
                if (ret)
                        goto out;

                read_lock_irq(&gpc->lock);
        }

        /*
         * This code mirrors kvm_write_wall_clock() except that it writes
         * directly through the pfn cache and doesn't mark the page dirty.
         */
        wall_nsec = kvm_get_wall_clock_epoch(kvm);

        /* Paranoia checks on the 32-bit struct layout */
        BUILD_BUG_ON(offsetof(struct compat_shared_info, wc) != 0x900);
        BUILD_BUG_ON(offsetof(struct compat_shared_info, arch.wc_sec_hi) != 0x924);
        BUILD_BUG_ON(offsetof(struct pvclock_vcpu_time_info, version) != 0);

#ifdef CONFIG_X86_64
        /* Paranoia checks on the 64-bit struct layout */
        BUILD_BUG_ON(offsetof(struct shared_info, wc) != 0xc00);
        BUILD_BUG_ON(offsetof(struct shared_info, wc_sec_hi) != 0xc0c);

        if (IS_ENABLED(CONFIG_64BIT) && kvm->arch.xen.long_mode) {
                struct shared_info *shinfo = gpc->khva;

                wc_sec_hi = &shinfo->wc_sec_hi;
                wc = &shinfo->wc;
        } else
#endif
        {
                struct compat_shared_info *shinfo = gpc->khva;

                wc_sec_hi = &shinfo->arch.wc_sec_hi;
                wc = &shinfo->wc;
        }

        /* Increment and ensure an odd value */
        wc_version = wc->version = (wc->version + 1) | 1;
        smp_wmb();

        wc->nsec = do_div(wall_nsec, NSEC_PER_SEC);
        wc->sec = (u32)wall_nsec;
        *wc_sec_hi = wall_nsec >> 32;
        smp_wmb();

        wc->version = wc_version + 1;
        read_unlock_irq(&gpc->lock);

        kvm_make_all_cpus_request(kvm, KVM_REQ_MASTERCLOCK_UPDATE);

out:
        srcu_read_unlock(&kvm->srcu, idx);
        return ret;
}

void kvm_xen_inject_timer_irqs(struct kvm_vcpu *vcpu)
{
        if (atomic_read(&vcpu->arch.xen.timer_pending) > 0) {
                struct kvm_xen_evtchn e;

                e.vcpu_id = vcpu->vcpu_id;
                e.vcpu_idx = vcpu->vcpu_idx;
                e.port = vcpu->arch.xen.timer_virq;
                e.priority = KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL;

                kvm_xen_set_evtchn(&e, vcpu->kvm);

                vcpu->arch.xen.timer_expires = 0;
                atomic_set(&vcpu->arch.xen.timer_pending, 0);
        }
}

static enum hrtimer_restart xen_timer_callback(struct hrtimer *timer)
{
        struct kvm_vcpu *vcpu = container_of(timer, struct kvm_vcpu,
                                             arch.xen.timer);
        struct kvm_xen_evtchn e;
        int rc;

        if (atomic_read(&vcpu->arch.xen.timer_pending))
                return HRTIMER_NORESTART;

        e.vcpu_id = vcpu->vcpu_id;
        e.vcpu_idx = vcpu->vcpu_idx;
        e.port = vcpu->arch.xen.timer_virq;
        e.priority = KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL;

        rc = kvm_xen_set_evtchn_fast(&e, vcpu->kvm);
        if (rc != -EWOULDBLOCK) {
                vcpu->arch.xen.timer_expires = 0;
                return HRTIMER_NORESTART;
        }

        atomic_inc(&vcpu->arch.xen.timer_pending);
        kvm_make_request(KVM_REQ_UNBLOCK, vcpu);
        kvm_vcpu_kick(vcpu);

        return HRTIMER_NORESTART;
}

static void kvm_xen_start_timer(struct kvm_vcpu *vcpu, u64 guest_abs,
                                bool linux_wa)
{
        int64_t kernel_now, delta;
        uint64_t guest_now;

        /*
         * The guest provides the requested timeout in absolute nanoseconds
         * of the KVM clock — as *it* sees it, based on the scaled TSC and
         * the pvclock information provided by KVM.
         *
         * The kernel doesn't support hrtimers based on CLOCK_MONOTONIC_RAW
         * so use CLOCK_MONOTONIC. In the timescales covered by timers, the
         * difference won't matter much as there is no cumulative effect.
         *
         * Calculate the time for some arbitrary point in time around "now"
         * in terms of both kvmclock and CLOCK_MONOTONIC. Calculate the
         * delta between the kvmclock "now" value and the guest's requested
         * timeout, apply the "Linux workaround" described below, and add
         * the resulting delta to the CLOCK_MONOTONIC "now" value, to get
         * the absolute CLOCK_MONOTONIC time at which the timer should
         * fire.
         */
        if (vcpu->arch.hv_clock.version && vcpu->kvm->arch.use_master_clock &&
            static_cpu_has(X86_FEATURE_CONSTANT_TSC)) {
                uint64_t host_tsc, guest_tsc;

                if (!IS_ENABLED(CONFIG_64BIT) ||
                    !kvm_get_monotonic_and_clockread(&kernel_now, &host_tsc)) {
                        /*
                         * Don't fall back to get_kvmclock_ns() because it's
                         * broken; it has a systemic error in its results
                         * because it scales directly from host TSC to
                         * nanoseconds, and doesn't scale first to guest TSC
                         * and *then* to nanoseconds as the guest does.
                         *
                         * There is a small error introduced here because time
                         * continues to elapse between the ktime_get() and the
                         * subsequent rdtsc(). But not the systemic drift due
                         * to get_kvmclock_ns().
                         */
                        kernel_now = ktime_get(); /* This is CLOCK_MONOTONIC */
                        host_tsc = rdtsc();
                }

                /* Calculate the guest kvmclock as the guest would do it. */
                guest_tsc = kvm_read_l1_tsc(vcpu, host_tsc);
                guest_now = __pvclock_read_cycles(&vcpu->arch.hv_clock,
                                                  guest_tsc);
        } else {
                /*
                 * Without CONSTANT_TSC, get_kvmclock_ns() is the only option.
                 *
                 * Also if the guest PV clock hasn't been set up yet, as is
                 * likely to be the case during migration when the vCPU has
                 * not been run yet. It would be possible to calculate the
                 * scaling factors properly in that case but there's not much
                 * point in doing so. The get_kvmclock_ns() drift accumulates
                 * over time, so it's OK to use it at startup. Besides, on
                 * migration there's going to be a little bit of skew in the
                 * precise moment at which timers fire anyway. Often they'll
                 * be in the "past" by the time the VM is running again after
                 * migration.
                 */
                guest_now = get_kvmclock_ns(vcpu->kvm);
                kernel_now = ktime_get();
        }

        delta = guest_abs - guest_now;

        /*
         * Xen has a 'Linux workaround' in do_set_timer_op() which checks for
         * negative absolute timeout values (caused by integer overflow), and
         * for values about 13 days in the future (2^50ns) which would be
         * caused by jiffies overflow. For those cases, Xen sets the timeout
         * 100ms in the future (not *too* soon, since if a guest really did
         * set a long timeout on purpose we don't want to keep churning CPU
         * time by waking it up).  Emulate Xen's workaround when starting the
         * timer in response to __HYPERVISOR_set_timer_op.
         */
        if (linux_wa &&
            unlikely((int64_t)guest_abs < 0 ||
                     (delta > 0 && (uint32_t) (delta >> 50) != 0))) {
                delta = 100 * NSEC_PER_MSEC;
                guest_abs = guest_now + delta;
        }

        /*
         * Avoid races with the old timer firing. Checking timer_expires
         * to avoid calling hrtimer_cancel() will only have false positives
         * so is fine.
         */
        if (vcpu->arch.xen.timer_expires)
                hrtimer_cancel(&vcpu->arch.xen.timer);

        atomic_set(&vcpu->arch.xen.timer_pending, 0);
        vcpu->arch.xen.timer_expires = guest_abs;

        if (delta <= 0)
                xen_timer_callback(&vcpu->arch.xen.timer);
        else
                hrtimer_start(&vcpu->arch.xen.timer,
                              ktime_add_ns(kernel_now, delta),
                              HRTIMER_MODE_ABS_HARD);
}

static void kvm_xen_stop_timer(struct kvm_vcpu *vcpu)
{
        hrtimer_cancel(&vcpu->arch.xen.timer);
        vcpu->arch.xen.timer_expires = 0;
        atomic_set(&vcpu->arch.xen.timer_pending, 0);
}

static void kvm_xen_update_runstate_guest(struct kvm_vcpu *v, bool atomic)
{
        struct kvm_vcpu_xen *vx = &v->arch.xen;
        struct gfn_to_pfn_cache *gpc1 = &vx->runstate_cache;
        struct gfn_to_pfn_cache *gpc2 = &vx->runstate2_cache;
        size_t user_len, user_len1, user_len2;
        struct vcpu_runstate_info rs;
        unsigned long flags;
        size_t times_ofs;
        uint8_t *update_bit = NULL;
        uint64_t entry_time;
        uint64_t *rs_times;
        int *rs_state;

        /*
         * The only difference between 32-bit and 64-bit versions of the
         * runstate struct is the alignment of uint64_t in 32-bit, which
         * means that the 64-bit version has an additional 4 bytes of
         * padding after the first field 'state'. Let's be really really
         * paranoid about that, and matching it with our internal data
         * structures that we memcpy into it...
         */
        BUILD_BUG_ON(offsetof(struct vcpu_runstate_info, state) != 0);
        BUILD_BUG_ON(offsetof(struct compat_vcpu_runstate_info, state) != 0);
        BUILD_BUG_ON(sizeof(struct compat_vcpu_runstate_info) != 0x2c);
#ifdef CONFIG_X86_64
        /*
         * The 64-bit structure has 4 bytes of padding before 'state_entry_time'
         * so each subsequent field is shifted by 4, and it's 4 bytes longer.
         */
        BUILD_BUG_ON(offsetof(struct vcpu_runstate_info, state_entry_time) !=
                     offsetof(struct compat_vcpu_runstate_info, state_entry_time) + 4);
        BUILD_BUG_ON(offsetof(struct vcpu_runstate_info, time) !=
                     offsetof(struct compat_vcpu_runstate_info, time) + 4);
        BUILD_BUG_ON(sizeof(struct vcpu_runstate_info) != 0x2c + 4);
#endif
        /*
         * The state field is in the same place at the start of both structs,
         * and is the same size (int) as vx->current_runstate.
         */
        BUILD_BUG_ON(offsetof(struct vcpu_runstate_info, state) !=
                     offsetof(struct compat_vcpu_runstate_info, state));
        BUILD_BUG_ON(sizeof_field(struct vcpu_runstate_info, state) !=
                     sizeof(vx->current_runstate));
        BUILD_BUG_ON(sizeof_field(struct compat_vcpu_runstate_info, state) !=
                     sizeof(vx->current_runstate));

        /*
         * The state_entry_time field is 64 bits in both versions, and the
         * XEN_RUNSTATE_UPDATE flag is in the top bit, which given that x86
         * is little-endian means that it's in the last *byte* of the word.
         * That detail is important later.
         */
        BUILD_BUG_ON(sizeof_field(struct vcpu_runstate_info, state_entry_time) !=
                     sizeof(uint64_t));
        BUILD_BUG_ON(sizeof_field(struct compat_vcpu_runstate_info, state_entry_time) !=
                     sizeof(uint64_t));
        BUILD_BUG_ON((XEN_RUNSTATE_UPDATE >> 56) != 0x80);

        /*
         * The time array is four 64-bit quantities in both versions, matching
         * the vx->runstate_times and immediately following state_entry_time.
         */
        BUILD_BUG_ON(offsetof(struct vcpu_runstate_info, state_entry_time) !=
                     offsetof(struct vcpu_runstate_info, time) - sizeof(uint64_t));
        BUILD_BUG_ON(offsetof(struct compat_vcpu_runstate_info, state_entry_time) !=
                     offsetof(struct compat_vcpu_runstate_info, time) - sizeof(uint64_t));
        BUILD_BUG_ON(sizeof_field(struct vcpu_runstate_info, time) !=
                     sizeof_field(struct compat_vcpu_runstate_info, time));
        BUILD_BUG_ON(sizeof_field(struct vcpu_runstate_info, time) !=
                     sizeof(vx->runstate_times));

        if (IS_ENABLED(CONFIG_64BIT) && v->kvm->arch.xen.long_mode) {
                user_len = sizeof(struct vcpu_runstate_info);
                times_ofs = offsetof(struct vcpu_runstate_info,
                                     state_entry_time);
        } else {
                user_len = sizeof(struct compat_vcpu_runstate_info);
                times_ofs = offsetof(struct compat_vcpu_runstate_info,
                                     state_entry_time);
        }

        /*
         * There are basically no alignment constraints. The guest can set it
         * up so it crosses from one page to the next, and at arbitrary byte
         * alignment (and the 32-bit ABI doesn't align the 64-bit integers
         * anyway, even if the overall struct had been 64-bit aligned).
         */
        if ((gpc1->gpa & ~PAGE_MASK) + user_len >= PAGE_SIZE) {
                user_len1 = PAGE_SIZE - (gpc1->gpa & ~PAGE_MASK);
                user_len2 = user_len - user_len1;
        } else {
                user_len1 = user_len;
                user_len2 = 0;
        }
        BUG_ON(user_len1 + user_len2 != user_len);

 retry:
        /*
         * Attempt to obtain the GPC lock on *both* (if there are two)
         * gfn_to_pfn caches that cover the region.
         */
        if (atomic) {
                local_irq_save(flags);
                if (!read_trylock(&gpc1->lock)) {
                        local_irq_restore(flags);
                        return;
                }
        } else {
                read_lock_irqsave(&gpc1->lock, flags);
        }
        while (!kvm_gpc_check(gpc1, user_len1)) {
                read_unlock_irqrestore(&gpc1->lock, flags);

                /* When invoked from kvm_sched_out() we cannot sleep */
                if (atomic)
                        return;

                if (kvm_gpc_refresh(gpc1, user_len1))
                        return;

                read_lock_irqsave(&gpc1->lock, flags);
        }

        if (likely(!user_len2)) {
                /*
                 * Set up three pointers directly to the runstate_info
                 * struct in the guest (via the GPC).
                 *
                 *  • @rs_state   → state field
                 *  • @rs_times   → state_entry_time field.
                 *  • @update_bit → last byte of state_entry_time, which
                 *                  contains the XEN_RUNSTATE_UPDATE bit.
                 */
                rs_state = gpc1->khva;
                rs_times = gpc1->khva + times_ofs;
                if (v->kvm->arch.xen.runstate_update_flag)
                        update_bit = ((void *)(&rs_times[1])) - 1;
        } else {
                /*
                 * The guest's runstate_info is split across two pages and we
                 * need to hold and validate both GPCs simultaneously. We can
                 * declare a lock ordering GPC1 > GPC2 because nothing else
                 * takes them more than one at a time. Set a subclass on the
                 * gpc1 lock to make lockdep shut up about it.
                 */
                lock_set_subclass(&gpc1->lock.dep_map, 1, _THIS_IP_);
                if (atomic) {
                        if (!read_trylock(&gpc2->lock)) {
                                read_unlock_irqrestore(&gpc1->lock, flags);
                                return;
                        }
                } else {
                        read_lock(&gpc2->lock);
                }

                if (!kvm_gpc_check(gpc2, user_len2)) {
                        read_unlock(&gpc2->lock);
                        read_unlock_irqrestore(&gpc1->lock, flags);

                        /* When invoked from kvm_sched_out() we cannot sleep */
                        if (atomic)
                                return;

                        /*
                         * Use kvm_gpc_activate() here because if the runstate
                         * area was configured in 32-bit mode and only extends
                         * to the second page now because the guest changed to
                         * 64-bit mode, the second GPC won't have been set up.
                         */
                        if (kvm_gpc_activate(gpc2, gpc1->gpa + user_len1,
                                             user_len2))
                                return;

                        /*
                         * We dropped the lock on GPC1 so we have to go all the
                         * way back and revalidate that too.
                         */
                        goto retry;
                }

                /*
                 * In this case, the runstate_info struct will be assembled on
                 * the kernel stack (compat or not as appropriate) and will
                 * be copied to GPC1/GPC2 with a dual memcpy. Set up the three
                 * rs pointers accordingly.
                 */
                rs_times = &rs.state_entry_time;

                /*
                 * The rs_state pointer points to the start of what we'll
                 * copy to the guest, which in the case of a compat guest
                 * is the 32-bit field that the compiler thinks is padding.
                 */
                rs_state = ((void *)rs_times) - times_ofs;

                /*
                 * The update_bit is still directly in the guest memory,
                 * via one GPC or the other.
                 */
                if (v->kvm->arch.xen.runstate_update_flag) {
                        if (user_len1 >= times_ofs + sizeof(uint64_t))
                                update_bit = gpc1->khva + times_ofs +
                                        sizeof(uint64_t) - 1;
                        else
                                update_bit = gpc2->khva + times_ofs +
                                        sizeof(uint64_t) - 1 - user_len1;
                }

#ifdef CONFIG_X86_64
                /*
                 * Don't leak kernel memory through the padding in the 64-bit
                 * version of the struct.
                 */
                memset(&rs, 0, offsetof(struct vcpu_runstate_info, state_entry_time));
#endif
        }

        /*
         * First, set the XEN_RUNSTATE_UPDATE bit in the top bit of the
         * state_entry_time field, directly in the guest. We need to set
         * that (and write-barrier) before writing to the rest of the
         * structure, and clear it last. Just as Xen does, we address the
         * single *byte* in which it resides because it might be in a
         * different cache line to the rest of the 64-bit word, due to
         * the (lack of) alignment constraints.
         */
        entry_time = vx->runstate_entry_time;
        if (update_bit) {
                entry_time |= XEN_RUNSTATE_UPDATE;
                *update_bit = (vx->runstate_entry_time | XEN_RUNSTATE_UPDATE) >> 56;
                smp_wmb();
        }

        /*
         * Now assemble the actual structure, either on our kernel stack
         * or directly in the guest according to how the rs_state and
         * rs_times pointers were set up above.
         */
        *rs_state = vx->current_runstate;
        rs_times[0] = entry_time;
        memcpy(rs_times + 1, vx->runstate_times, sizeof(vx->runstate_times));

        /* For the split case, we have to then copy it to the guest. */
        if (user_len2) {
                memcpy(gpc1->khva, rs_state, user_len1);
                memcpy(gpc2->khva, ((void *)rs_state) + user_len1, user_len2);
        }
        smp_wmb();

        /* Finally, clear the XEN_RUNSTATE_UPDATE bit. */
        if (update_bit) {
                entry_time &= ~XEN_RUNSTATE_UPDATE;
                *update_bit = entry_time >> 56;
                smp_wmb();
        }

        if (user_len2) {
                kvm_gpc_mark_dirty_in_slot(gpc2);
                read_unlock(&gpc2->lock);
        }

        kvm_gpc_mark_dirty_in_slot(gpc1);
        read_unlock_irqrestore(&gpc1->lock, flags);
}

void kvm_xen_update_runstate(struct kvm_vcpu *v, int state)
{
        struct kvm_vcpu_xen *vx = &v->arch.xen;
        u64 now = get_kvmclock_ns(v->kvm);
        u64 delta_ns = now - vx->runstate_entry_time;
        u64 run_delay = current->sched_info.run_delay;

        if (unlikely(!vx->runstate_entry_time))
                vx->current_runstate = RUNSTATE_offline;

        /*
         * Time waiting for the scheduler isn't "stolen" if the
         * vCPU wasn't running anyway.
         */
        if (vx->current_runstate == RUNSTATE_running) {
                u64 steal_ns = run_delay - vx->last_steal;

                delta_ns -= steal_ns;

                vx->runstate_times[RUNSTATE_runnable] += steal_ns;
        }
        vx->last_steal = run_delay;

        vx->runstate_times[vx->current_runstate] += delta_ns;
        vx->current_runstate = state;
        vx->runstate_entry_time = now;

        if (vx->runstate_cache.active)
                kvm_xen_update_runstate_guest(v, state == RUNSTATE_runnable);
}

void kvm_xen_inject_vcpu_vector(struct kvm_vcpu *v)
{
        struct kvm_lapic_irq irq = { };

        irq.dest_id = v->vcpu_id;
        irq.vector = v->arch.xen.upcall_vector;
        irq.dest_mode = APIC_DEST_PHYSICAL;
        irq.shorthand = APIC_DEST_NOSHORT;
        irq.delivery_mode = APIC_DM_FIXED;
        irq.level = 1;

        kvm_irq_delivery_to_apic(v->kvm, NULL, &irq, NULL);
}

/*
 * On event channel delivery, the vcpu_info may not have been accessible.
 * In that case, there are bits in vcpu->arch.xen.evtchn_pending_sel which
 * need to be marked into the vcpu_info (and evtchn_upcall_pending set).
 * Do so now that we can sleep in the context of the vCPU to bring the
 * page in, and refresh the pfn cache for it.
 */
void kvm_xen_inject_pending_events(struct kvm_vcpu *v)
{
        unsigned long evtchn_pending_sel = READ_ONCE(v->arch.xen.evtchn_pending_sel);
        struct gfn_to_pfn_cache *gpc = &v->arch.xen.vcpu_info_cache;
        unsigned long flags;

        if (!evtchn_pending_sel)
                return;

        /*
         * Yes, this is an open-coded loop. But that's just what put_user()
         * does anyway. Page it in and retry the instruction. We're just a
         * little more honest about it.
         */
        read_lock_irqsave(&gpc->lock, flags);
        while (!kvm_gpc_check(gpc, sizeof(struct vcpu_info))) {
                read_unlock_irqrestore(&gpc->lock, flags);

                if (kvm_gpc_refresh(gpc, sizeof(struct vcpu_info)))
                        return;

                read_lock_irqsave(&gpc->lock, flags);
        }

        /* Now gpc->khva is a valid kernel address for the vcpu_info */
        if (IS_ENABLED(CONFIG_64BIT) && v->kvm->arch.xen.long_mode) {
                struct vcpu_info *vi = gpc->khva;

                asm volatile(LOCK_PREFIX "orq %0, %1\n"
                             "notq %0\n"
                             LOCK_PREFIX "andq %0, %2\n"
                             : "=r" (evtchn_pending_sel),
                               "+m" (vi->evtchn_pending_sel),
                               "+m" (v->arch.xen.evtchn_pending_sel)
                             : "0" (evtchn_pending_sel));
                WRITE_ONCE(vi->evtchn_upcall_pending, 1);
        } else {
                u32 evtchn_pending_sel32 = evtchn_pending_sel;
                struct compat_vcpu_info *vi = gpc->khva;

                asm volatile(LOCK_PREFIX "orl %0, %1\n"
                             "notl %0\n"
                             LOCK_PREFIX "andl %0, %2\n"
                             : "=r" (evtchn_pending_sel32),
                               "+m" (vi->evtchn_pending_sel),
                               "+m" (v->arch.xen.evtchn_pending_sel)
                             : "0" (evtchn_pending_sel32));
                WRITE_ONCE(vi->evtchn_upcall_pending, 1);
        }

        kvm_gpc_mark_dirty_in_slot(gpc);
        read_unlock_irqrestore(&gpc->lock, flags);

        /* For the per-vCPU lapic vector, deliver it as MSI. */
        if (v->arch.xen.upcall_vector)
                kvm_xen_inject_vcpu_vector(v);
}

int __kvm_xen_has_interrupt(struct kvm_vcpu *v)
{
        struct gfn_to_pfn_cache *gpc = &v->arch.xen.vcpu_info_cache;
        unsigned long flags;
        u8 rc = 0;

        /*
         * If the global upcall vector (HVMIRQ_callback_vector) is set and
         * the vCPU's evtchn_upcall_pending flag is set, the IRQ is pending.
         */

        /* No need for compat handling here */
        BUILD_BUG_ON(offsetof(struct vcpu_info, evtchn_upcall_pending) !=
                     offsetof(struct compat_vcpu_info, evtchn_upcall_pending));
        BUILD_BUG_ON(sizeof(rc) !=
                     sizeof_field(struct vcpu_info, evtchn_upcall_pending));
        BUILD_BUG_ON(sizeof(rc) !=
                     sizeof_field(struct compat_vcpu_info, evtchn_upcall_pending));

        read_lock_irqsave(&gpc->lock, flags);
        while (!kvm_gpc_check(gpc, sizeof(struct vcpu_info))) {
                read_unlock_irqrestore(&gpc->lock, flags);

                /*
                 * This function gets called from kvm_vcpu_block() after setting the
                 * task to TASK_INTERRUPTIBLE, to see if it needs to wake immediately
                 * from a HLT. So we really mustn't sleep. If the page ended up absent
                 * at that point, just return 1 in order to trigger an immediate wake,
                 * and we'll end up getting called again from a context where we *can*
                 * fault in the page and wait for it.
                 */
                if (in_atomic() || !task_is_running(current))
                        return 1;

                if (kvm_gpc_refresh(gpc, sizeof(struct vcpu_info))) {
                        /*
                         * If this failed, userspace has screwed up the
                         * vcpu_info mapping. No interrupts for you.
                         */
                        return 0;
                }
                read_lock_irqsave(&gpc->lock, flags);
        }

        rc = ((struct vcpu_info *)gpc->khva)->evtchn_upcall_pending;
        read_unlock_irqrestore(&gpc->lock, flags);
        return rc;
}

int kvm_xen_hvm_set_attr(struct kvm *kvm, struct kvm_xen_hvm_attr *data)
{
        int r = -ENOENT;


        switch (data->type) {
        case KVM_XEN_ATTR_TYPE_LONG_MODE:
                if (!IS_ENABLED(CONFIG_64BIT) && data->u.long_mode) {
                        r = -EINVAL;
                } else {
                        mutex_lock(&kvm->arch.xen.xen_lock);
                        kvm->arch.xen.long_mode = !!data->u.long_mode;

                        /*
                         * Re-initialize shared_info to put the wallclock in the
                         * correct place. Whilst it's not necessary to do this
                         * unless the mode is actually changed, it does no harm
                         * to make the call anyway.
                         */
                        r = kvm->arch.xen.shinfo_cache.active ?
                                kvm_xen_shared_info_init(kvm) : 0;
                        mutex_unlock(&kvm->arch.xen.xen_lock);
                }
                break;

        case KVM_XEN_ATTR_TYPE_SHARED_INFO:
        case KVM_XEN_ATTR_TYPE_SHARED_INFO_HVA: {
                int idx;

                mutex_lock(&kvm->arch.xen.xen_lock);

                idx = srcu_read_lock(&kvm->srcu);

                if (data->type == KVM_XEN_ATTR_TYPE_SHARED_INFO) {
                        gfn_t gfn = data->u.shared_info.gfn;

                        if (gfn == KVM_XEN_INVALID_GFN) {
                                kvm_gpc_deactivate(&kvm->arch.xen.shinfo_cache);
                                r = 0;
                        } else {
                                r = kvm_gpc_activate(&kvm->arch.xen.shinfo_cache,
                                                     gfn_to_gpa(gfn), PAGE_SIZE);
                        }
                } else {
                        void __user * hva = u64_to_user_ptr(data->u.shared_info.hva);

                        if (!PAGE_ALIGNED(hva)) {
                                r = -EINVAL;
                        } else if (!hva) {
                                kvm_gpc_deactivate(&kvm->arch.xen.shinfo_cache);
                                r = 0;
                        } else {
                                r = kvm_gpc_activate_hva(&kvm->arch.xen.shinfo_cache,
                                                         (unsigned long)hva, PAGE_SIZE);
                        }
                }

                srcu_read_unlock(&kvm->srcu, idx);

                if (!r && kvm->arch.xen.shinfo_cache.active)
                        r = kvm_xen_shared_info_init(kvm);

                mutex_unlock(&kvm->arch.xen.xen_lock);
                break;
        }
        case KVM_XEN_ATTR_TYPE_UPCALL_VECTOR:
                if (data->u.vector && data->u.vector < 0x10)
                        r = -EINVAL;
                else {
                        mutex_lock(&kvm->arch.xen.xen_lock);
                        kvm->arch.xen.upcall_vector = data->u.vector;
                        mutex_unlock(&kvm->arch.xen.xen_lock);
                        r = 0;
                }
                break;

        case KVM_XEN_ATTR_TYPE_EVTCHN:
                r = kvm_xen_setattr_evtchn(kvm, data);
                break;

        case KVM_XEN_ATTR_TYPE_XEN_VERSION:
                mutex_lock(&kvm->arch.xen.xen_lock);
                kvm->arch.xen.xen_version = data->u.xen_version;
                mutex_unlock(&kvm->arch.xen.xen_lock);
                r = 0;
                break;

        case KVM_XEN_ATTR_TYPE_RUNSTATE_UPDATE_FLAG:
                if (!sched_info_on()) {
                        r = -EOPNOTSUPP;
                        break;
                }
                mutex_lock(&kvm->arch.xen.xen_lock);
                kvm->arch.xen.runstate_update_flag = !!data->u.runstate_update_flag;
                mutex_unlock(&kvm->arch.xen.xen_lock);
                r = 0;
                break;

        default:
                break;
        }

        return r;
}

int kvm_xen_hvm_get_attr(struct kvm *kvm, struct kvm_xen_hvm_attr *data)
{
        int r = -ENOENT;

        mutex_lock(&kvm->arch.xen.xen_lock);

        switch (data->type) {
        case KVM_XEN_ATTR_TYPE_LONG_MODE:
                data->u.long_mode = kvm->arch.xen.long_mode;
                r = 0;
                break;

        case KVM_XEN_ATTR_TYPE_SHARED_INFO:
                if (kvm_gpc_is_gpa_active(&kvm->arch.xen.shinfo_cache))
                        data->u.shared_info.gfn = gpa_to_gfn(kvm->arch.xen.shinfo_cache.gpa);
                else
                        data->u.shared_info.gfn = KVM_XEN_INVALID_GFN;
                r = 0;
                break;

        case KVM_XEN_ATTR_TYPE_SHARED_INFO_HVA:
                if (kvm_gpc_is_hva_active(&kvm->arch.xen.shinfo_cache))
                        data->u.shared_info.hva = kvm->arch.xen.shinfo_cache.uhva;
                else
                        data->u.shared_info.hva = 0;
                r = 0;
                break;

        case KVM_XEN_ATTR_TYPE_UPCALL_VECTOR:
                data->u.vector = kvm->arch.xen.upcall_vector;
                r = 0;
                break;

        case KVM_XEN_ATTR_TYPE_XEN_VERSION:
                data->u.xen_version = kvm->arch.xen.xen_version;
                r = 0;
                break;

        case KVM_XEN_ATTR_TYPE_RUNSTATE_UPDATE_FLAG:
                if (!sched_info_on()) {
                        r = -EOPNOTSUPP;
                        break;
                }
                data->u.runstate_update_flag = kvm->arch.xen.runstate_update_flag;
                r = 0;
                break;

        default:
                break;
        }

        mutex_unlock(&kvm->arch.xen.xen_lock);
        return r;
}

int kvm_xen_vcpu_set_attr(struct kvm_vcpu *vcpu, struct kvm_xen_vcpu_attr *data)
{
        int idx, r = -ENOENT;

        mutex_lock(&vcpu->kvm->arch.xen.xen_lock);
        idx = srcu_read_lock(&vcpu->kvm->srcu);

        switch (data->type) {
        case KVM_XEN_VCPU_ATTR_TYPE_VCPU_INFO:
        case KVM_XEN_VCPU_ATTR_TYPE_VCPU_INFO_HVA:
                /* No compat necessary here. */
                BUILD_BUG_ON(sizeof(struct vcpu_info) !=
                             sizeof(struct compat_vcpu_info));
                BUILD_BUG_ON(offsetof(struct vcpu_info, time) !=
                             offsetof(struct compat_vcpu_info, time));

                if (data->type == KVM_XEN_VCPU_ATTR_TYPE_VCPU_INFO) {
                        if (data->u.gpa == KVM_XEN_INVALID_GPA) {
                                kvm_gpc_deactivate(&vcpu->arch.xen.vcpu_info_cache);
                                r = 0;
                                break;
                        }

                        r = kvm_gpc_activate(&vcpu->arch.xen.vcpu_info_cache,
                                             data->u.gpa, sizeof(struct vcpu_info));
                } else {
                        if (data->u.hva == 0) {
                                kvm_gpc_deactivate(&vcpu->arch.xen.vcpu_info_cache);
                                r = 0;
                                break;
                        }

                        r = kvm_gpc_activate_hva(&vcpu->arch.xen.vcpu_info_cache,
                                                 data->u.hva, sizeof(struct vcpu_info));
                }

                if (!r)
                        kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu);

                break;

        case KVM_XEN_VCPU_ATTR_TYPE_VCPU_TIME_INFO:
                if (data->u.gpa == KVM_XEN_INVALID_GPA) {
                        kvm_gpc_deactivate(&vcpu->arch.xen.vcpu_time_info_cache);
                        r = 0;
                        break;
                }

                r = kvm_gpc_activate(&vcpu->arch.xen.vcpu_time_info_cache,
                                     data->u.gpa,
                                     sizeof(struct pvclock_vcpu_time_info));
                if (!r)
                        kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu);
                break;

        case KVM_XEN_VCPU_ATTR_TYPE_RUNSTATE_ADDR: {
                size_t sz, sz1, sz2;

                if (!sched_info_on()) {
                        r = -EOPNOTSUPP;
                        break;
                }
                if (data->u.gpa == KVM_XEN_INVALID_GPA) {
                        r = 0;
                deactivate_out:
                        kvm_gpc_deactivate(&vcpu->arch.xen.runstate_cache);
                        kvm_gpc_deactivate(&vcpu->arch.xen.runstate2_cache);
                        break;
                }

                /*
                 * If the guest switches to 64-bit mode after setting the runstate
                 * address, that's actually OK. kvm_xen_update_runstate_guest()
                 * will cope.
                 */
                if (IS_ENABLED(CONFIG_64BIT) && vcpu->kvm->arch.xen.long_mode)
                        sz = sizeof(struct vcpu_runstate_info);
                else
                        sz = sizeof(struct compat_vcpu_runstate_info);

                /* How much fits in the (first) page? */
                sz1 = PAGE_SIZE - (data->u.gpa & ~PAGE_MASK);
                r = kvm_gpc_activate(&vcpu->arch.xen.runstate_cache,
                                     data->u.gpa, sz1);
                if (r)
                        goto deactivate_out;

                /* Either map the second page, or deactivate the second GPC */
                if (sz1 >= sz) {
                        kvm_gpc_deactivate(&vcpu->arch.xen.runstate2_cache);
                } else {
                        sz2 = sz - sz1;
                        BUG_ON((data->u.gpa + sz1) & ~PAGE_MASK);
                        r = kvm_gpc_activate(&vcpu->arch.xen.runstate2_cache,
                                             data->u.gpa + sz1, sz2);
                        if (r)
                                goto deactivate_out;
                }

                kvm_xen_update_runstate_guest(vcpu, false);
                break;
        }
        case KVM_XEN_VCPU_ATTR_TYPE_RUNSTATE_CURRENT:
                if (!sched_info_on()) {
                        r = -EOPNOTSUPP;
                        break;
                }
                if (data->u.runstate.state > RUNSTATE_offline) {
                        r = -EINVAL;
                        break;
                }

                kvm_xen_update_runstate(vcpu, data->u.runstate.state);
                r = 0;
                break;

        case KVM_XEN_VCPU_ATTR_TYPE_RUNSTATE_DATA:
                if (!sched_info_on()) {
                        r = -EOPNOTSUPP;
                        break;
                }
                if (data->u.runstate.state > RUNSTATE_offline) {
                        r = -EINVAL;
                        break;
                }
                if (data->u.runstate.state_entry_time !=
                    (data->u.runstate.time_running +
                     data->u.runstate.time_runnable +
                     data->u.runstate.time_blocked +
                     data->u.runstate.time_offline)) {
                        r = -EINVAL;
                        break;
                }
                if (get_kvmclock_ns(vcpu->kvm) <
                    data->u.runstate.state_entry_time) {
                        r = -EINVAL;
                        break;
                }

                vcpu->arch.xen.current_runstate = data->u.runstate.state;
                vcpu->arch.xen.runstate_entry_time =
                        data->u.runstate.state_entry_time;
                vcpu->arch.xen.runstate_times[RUNSTATE_running] =
                        data->u.runstate.time_running;
                vcpu->arch.xen.runstate_times[RUNSTATE_runnable] =
                        data->u.runstate.time_runnable;
                vcpu->arch.xen.runstate_times[RUNSTATE_blocked] =
                        data->u.runstate.time_blocked;
                vcpu->arch.xen.runstate_times[RUNSTATE_offline] =
                        data->u.runstate.time_offline;
                vcpu->arch.xen.last_steal = current->sched_info.run_delay;
                r = 0;
                break;

        case KVM_XEN_VCPU_ATTR_TYPE_RUNSTATE_ADJUST:
                if (!sched_info_on()) {
                        r = -EOPNOTSUPP;
                        break;
                }
                if (data->u.runstate.state > RUNSTATE_offline &&
                    data->u.runstate.state != (u64)-1) {
                        r = -EINVAL;
                        break;
                }
                /* The adjustment must add up */
                if (data->u.runstate.state_entry_time !=
                    (data->u.runstate.time_running +
                     data->u.runstate.time_runnable +
                     data->u.runstate.time_blocked +
                     data->u.runstate.time_offline)) {
                        r = -EINVAL;
                        break;
                }

                if (get_kvmclock_ns(vcpu->kvm) <
                    (vcpu->arch.xen.runstate_entry_time +
                     data->u.runstate.state_entry_time)) {
                        r = -EINVAL;
                        break;
                }

                vcpu->arch.xen.runstate_entry_time +=
                        data->u.runstate.state_entry_time;
                vcpu->arch.xen.runstate_times[RUNSTATE_running] +=
                        data->u.runstate.time_running;
                vcpu->arch.xen.runstate_times[RUNSTATE_runnable] +=
                        data->u.runstate.time_runnable;
                vcpu->arch.xen.runstate_times[RUNSTATE_blocked] +=
                        data->u.runstate.time_blocked;
                vcpu->arch.xen.runstate_times[RUNSTATE_offline] +=
                        data->u.runstate.time_offline;

                if (data->u.runstate.state <= RUNSTATE_offline)
                        kvm_xen_update_runstate(vcpu, data->u.runstate.state);
                else if (vcpu->arch.xen.runstate_cache.active)
                        kvm_xen_update_runstate_guest(vcpu, false);
                r = 0;
                break;

        case KVM_XEN_VCPU_ATTR_TYPE_VCPU_ID:
                if (data->u.vcpu_id >= KVM_MAX_VCPUS)
                        r = -EINVAL;
                else {
                        vcpu->arch.xen.vcpu_id = data->u.vcpu_id;
                        r = 0;
                }
                break;

        case KVM_XEN_VCPU_ATTR_TYPE_TIMER:
                if (data->u.timer.port &&
                    data->u.timer.priority != KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL) {
                        r = -EINVAL;
                        break;
                }

                /* Stop the timer (if it's running) before changing the vector */
                kvm_xen_stop_timer(vcpu);
                vcpu->arch.xen.timer_virq = data->u.timer.port;

                /* Start the timer if the new value has a valid vector+expiry. */
                if (data->u.timer.port && data->u.timer.expires_ns)
                        kvm_xen_start_timer(vcpu, data->u.timer.expires_ns, false);

                r = 0;
                break;

        case KVM_XEN_VCPU_ATTR_TYPE_UPCALL_VECTOR:
                if (data->u.vector && data->u.vector < 0x10)
                        r = -EINVAL;
                else {
                        vcpu->arch.xen.upcall_vector = data->u.vector;
                        r = 0;
                }
                break;

        default:
                break;
        }

        srcu_read_unlock(&vcpu->kvm->srcu, idx);
        mutex_unlock(&vcpu->kvm->arch.xen.xen_lock);
        return r;
}

int kvm_xen_vcpu_get_attr(struct kvm_vcpu *vcpu, struct kvm_xen_vcpu_attr *data)
{
        int r = -ENOENT;

        mutex_lock(&vcpu->kvm->arch.xen.xen_lock);

        switch (data->type) {
        case KVM_XEN_VCPU_ATTR_TYPE_VCPU_INFO:
                if (kvm_gpc_is_gpa_active(&vcpu->arch.xen.vcpu_info_cache))
                        data->u.gpa = vcpu->arch.xen.vcpu_info_cache.gpa;
                else
                        data->u.gpa = KVM_XEN_INVALID_GPA;
                r = 0;
                break;

        case KVM_XEN_VCPU_ATTR_TYPE_VCPU_INFO_HVA:
                if (kvm_gpc_is_hva_active(&vcpu->arch.xen.vcpu_info_cache))
                        data->u.hva = vcpu->arch.xen.vcpu_info_cache.uhva;
                else
                        data->u.hva = 0;
                r = 0;
                break;

        case KVM_XEN_VCPU_ATTR_TYPE_VCPU_TIME_INFO:
                if (vcpu->arch.xen.vcpu_time_info_cache.active)
                        data->u.gpa = vcpu->arch.xen.vcpu_time_info_cache.gpa;
                else
                        data->u.gpa = KVM_XEN_INVALID_GPA;
                r = 0;
                break;

        case KVM_XEN_VCPU_ATTR_TYPE_RUNSTATE_ADDR:
                if (!sched_info_on()) {
                        r = -EOPNOTSUPP;
                        break;
                }
                if (vcpu->arch.xen.runstate_cache.active) {
                        data->u.gpa = vcpu->arch.xen.runstate_cache.gpa;
                        r = 0;
                }
                break;

        case KVM_XEN_VCPU_ATTR_TYPE_RUNSTATE_CURRENT:
                if (!sched_info_on()) {
                        r = -EOPNOTSUPP;
                        break;
                }
                data->u.runstate.state = vcpu->arch.xen.current_runstate;
                r = 0;
                break;

        case KVM_XEN_VCPU_ATTR_TYPE_RUNSTATE_DATA:
                if (!sched_info_on()) {
                        r = -EOPNOTSUPP;
                        break;
                }
                data->u.runstate.state = vcpu->arch.xen.current_runstate;
                data->u.runstate.state_entry_time =
                        vcpu->arch.xen.runstate_entry_time;
                data->u.runstate.time_running =
                        vcpu->arch.xen.runstate_times[RUNSTATE_running];
                data->u.runstate.time_runnable =
                        vcpu->arch.xen.runstate_times[RUNSTATE_runnable];
                data->u.runstate.time_blocked =
                        vcpu->arch.xen.runstate_times[RUNSTATE_blocked];
                data->u.runstate.time_offline =
                        vcpu->arch.xen.runstate_times[RUNSTATE_offline];
                r = 0;
                break;

        case KVM_XEN_VCPU_ATTR_TYPE_RUNSTATE_ADJUST:
                r = -EINVAL;
                break;

        case KVM_XEN_VCPU_ATTR_TYPE_VCPU_ID:
                data->u.vcpu_id = vcpu->arch.xen.vcpu_id;
                r = 0;
                break;

        case KVM_XEN_VCPU_ATTR_TYPE_TIMER:
                /*
                 * Ensure a consistent snapshot of state is captured, with a
                 * timer either being pending, or the event channel delivered
                 * to the corresponding bit in the shared_info. Not still
                 * lurking in the timer_pending flag for deferred delivery.
                 * Purely as an optimisation, if the timer_expires field is
                 * zero, that means the timer isn't active (or even in the
                 * timer_pending flag) and there is no need to cancel it.
                 */
                if (vcpu->arch.xen.timer_expires) {
                        hrtimer_cancel(&vcpu->arch.xen.timer);
                        kvm_xen_inject_timer_irqs(vcpu);
                }

                data->u.timer.port = vcpu->arch.xen.timer_virq;
                data->u.timer.priority = KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL;
                data->u.timer.expires_ns = vcpu->arch.xen.timer_expires;

                /*
                 * The hrtimer may trigger and raise the IRQ immediately,
                 * while the returned state causes it to be set up and
                 * raised again on the destination system after migration.
                 * That's fine, as the guest won't even have had a chance
                 * to run and handle the interrupt. Asserting an already
                 * pending event channel is idempotent.
                 */
                if (vcpu->arch.xen.timer_expires)
                        hrtimer_start_expires(&vcpu->arch.xen.timer,
                                              HRTIMER_MODE_ABS_HARD);

                r = 0;
                break;

        case KVM_XEN_VCPU_ATTR_TYPE_UPCALL_VECTOR:
                data->u.vector = vcpu->arch.xen.upcall_vector;
                r = 0;
                break;

        default:
                break;
        }

        mutex_unlock(&vcpu->kvm->arch.xen.xen_lock);
        return r;
}

int kvm_xen_write_hypercall_page(struct kvm_vcpu *vcpu, u64 data)
{
        struct kvm *kvm = vcpu->kvm;
        u32 page_num = data & ~PAGE_MASK;
        u64 page_addr = data & PAGE_MASK;
        bool lm = is_long_mode(vcpu);
        int r = 0;

        mutex_lock(&kvm->arch.xen.xen_lock);
        if (kvm->arch.xen.long_mode != lm) {
                kvm->arch.xen.long_mode = lm;

                /*
                 * Re-initialize shared_info to put the wallclock in the
                 * correct place.
                 */
                if (kvm->arch.xen.shinfo_cache.active &&
                    kvm_xen_shared_info_init(kvm))
                        r = 1;
        }
        mutex_unlock(&kvm->arch.xen.xen_lock);

        if (r)
                return r;

        /*
         * If Xen hypercall intercept is enabled, fill the hypercall
         * page with VMCALL/VMMCALL instructions since that's what
         * we catch. Else the VMM has provided the hypercall pages
         * with instructions of its own choosing, so use those.
         */
        if (kvm_xen_hypercall_enabled(kvm)) {
                u8 instructions[32];
                int i;

                if (page_num)
                        return 1;

                /* mov imm32, %eax */
                instructions[0] = 0xb8;

                /* vmcall / vmmcall */
                kvm_x86_call(patch_hypercall)(vcpu, instructions + 5);

                /* ret */
                instructions[8] = 0xc3;

                /* int3 to pad */
                memset(instructions + 9, 0xcc, sizeof(instructions) - 9);

                for (i = 0; i < PAGE_SIZE / sizeof(instructions); i++) {
                        *(u32 *)&instructions[1] = i;
                        if (kvm_vcpu_write_guest(vcpu,
                                                 page_addr + (i * sizeof(instructions)),
                                                 instructions, sizeof(instructions)))
                                return 1;
                }
        } else {
                /*
                 * Note, truncation is a non-issue as 'lm' is guaranteed to be
                 * false for a 32-bit kernel, i.e. when hva_t is only 4 bytes.
                 */
                hva_t blob_addr = lm ? kvm->arch.xen_hvm_config.blob_addr_64
                                     : kvm->arch.xen_hvm_config.blob_addr_32;
                u8 blob_size = lm ? kvm->arch.xen_hvm_config.blob_size_64
                                  : kvm->arch.xen_hvm_config.blob_size_32;
                u8 *page;
                int ret;

                if (page_num >= blob_size)
                        return 1;

                blob_addr += page_num * PAGE_SIZE;

                page = memdup_user((u8 __user *)blob_addr, PAGE_SIZE);
                if (IS_ERR(page))
                        return PTR_ERR(page);

                ret = kvm_vcpu_write_guest(vcpu, page_addr, page, PAGE_SIZE);
                kfree(page);
                if (ret)
                        return 1;
        }
        return 0;
}

int kvm_xen_hvm_config(struct kvm *kvm, struct kvm_xen_hvm_config *xhc)
{
        /* Only some feature flags need to be *enabled* by userspace */
        u32 permitted_flags = KVM_XEN_HVM_CONFIG_INTERCEPT_HCALL |
                KVM_XEN_HVM_CONFIG_EVTCHN_SEND |
                KVM_XEN_HVM_CONFIG_PVCLOCK_TSC_UNSTABLE;
        u32 old_flags;

        if (xhc->flags & ~permitted_flags)
                return -EINVAL;

        /*
         * With hypercall interception the kernel generates its own
         * hypercall page so it must not be provided.
         */
        if ((xhc->flags & KVM_XEN_HVM_CONFIG_INTERCEPT_HCALL) &&
            (xhc->blob_addr_32 || xhc->blob_addr_64 ||
             xhc->blob_size_32 || xhc->blob_size_64))
                return -EINVAL;

        mutex_lock(&kvm->arch.xen.xen_lock);

        if (xhc->msr && !kvm->arch.xen_hvm_config.msr)
                static_branch_inc(&kvm_xen_enabled.key);
        else if (!xhc->msr && kvm->arch.xen_hvm_config.msr)
                static_branch_slow_dec_deferred(&kvm_xen_enabled);

        old_flags = kvm->arch.xen_hvm_config.flags;
        memcpy(&kvm->arch.xen_hvm_config, xhc, sizeof(*xhc));

        mutex_unlock(&kvm->arch.xen.xen_lock);

        if ((old_flags ^ xhc->flags) & KVM_XEN_HVM_CONFIG_PVCLOCK_TSC_UNSTABLE)
                kvm_make_all_cpus_request(kvm, KVM_REQ_CLOCK_UPDATE);

        return 0;
}

static int kvm_xen_hypercall_set_result(struct kvm_vcpu *vcpu, u64 result)
{
        kvm_rax_write(vcpu, result);
        return kvm_skip_emulated_instruction(vcpu);
}

static int kvm_xen_hypercall_complete_userspace(struct kvm_vcpu *vcpu)
{
        struct kvm_run *run = vcpu->run;

        if (unlikely(!kvm_is_linear_rip(vcpu, vcpu->arch.xen.hypercall_rip)))
                return 1;

        return kvm_xen_hypercall_set_result(vcpu, run->xen.u.hcall.result);
}

static inline int max_evtchn_port(struct kvm *kvm)
{
        if (IS_ENABLED(CONFIG_64BIT) && kvm->arch.xen.long_mode)
                return EVTCHN_2L_NR_CHANNELS;
        else
                return COMPAT_EVTCHN_2L_NR_CHANNELS;
}

static bool wait_pending_event(struct kvm_vcpu *vcpu, int nr_ports,
                               evtchn_port_t *ports)
{
        struct kvm *kvm = vcpu->kvm;
        struct gfn_to_pfn_cache *gpc = &kvm->arch.xen.shinfo_cache;
        unsigned long *pending_bits;
        unsigned long flags;
        bool ret = true;
        int idx, i;

        idx = srcu_read_lock(&kvm->srcu);
        read_lock_irqsave(&gpc->lock, flags);
        if (!kvm_gpc_check(gpc, PAGE_SIZE))
                goto out_rcu;

        ret = false;
        if (IS_ENABLED(CONFIG_64BIT) && kvm->arch.xen.long_mode) {
                struct shared_info *shinfo = gpc->khva;
                pending_bits = (unsigned long *)&shinfo->evtchn_pending;
        } else {
                struct compat_shared_info *shinfo = gpc->khva;
                pending_bits = (unsigned long *)&shinfo->evtchn_pending;
        }

        for (i = 0; i < nr_ports; i++) {
                if (test_bit(ports[i], pending_bits)) {
                        ret = true;
                        break;
                }
        }

 out_rcu:
        read_unlock_irqrestore(&gpc->lock, flags);
        srcu_read_unlock(&kvm->srcu, idx);

        return ret;
}

static bool kvm_xen_schedop_poll(struct kvm_vcpu *vcpu, bool longmode,
                                 u64 param, u64 *r)
{
        struct sched_poll sched_poll;
        evtchn_port_t port, *ports;
        struct x86_exception e;
        int i;

        if (!lapic_in_kernel(vcpu) ||
            !(vcpu->kvm->arch.xen_hvm_config.flags & KVM_XEN_HVM_CONFIG_EVTCHN_SEND))
                return false;

        if (IS_ENABLED(CONFIG_64BIT) && !longmode) {
                struct compat_sched_poll sp32;

                /* Sanity check that the compat struct definition is correct */
                BUILD_BUG_ON(sizeof(sp32) != 16);

                if (kvm_read_guest_virt(vcpu, param, &sp32, sizeof(sp32), &e)) {
                        *r = -EFAULT;
                        return true;
                }

                /*
                 * This is a 32-bit pointer to an array of evtchn_port_t which
                 * are uint32_t, so once it's converted no further compat
                 * handling is needed.
                 */
                sched_poll.ports = (void *)(unsigned long)(sp32.ports);
                sched_poll.nr_ports = sp32.nr_ports;
                sched_poll.timeout = sp32.timeout;
        } else {
                if (kvm_read_guest_virt(vcpu, param, &sched_poll,
                                        sizeof(sched_poll), &e)) {
                        *r = -EFAULT;
                        return true;
                }
        }

        if (unlikely(sched_poll.nr_ports > 1)) {
                /* Xen (unofficially) limits number of pollers to 128 */
                if (sched_poll.nr_ports > 128) {
                        *r = -EINVAL;
                        return true;
                }

                ports = kmalloc_array(sched_poll.nr_ports,
                                      sizeof(*ports), GFP_KERNEL);
                if (!ports) {
                        *r = -ENOMEM;
                        return true;
                }
        } else
                ports = &port;

        if (kvm_read_guest_virt(vcpu, (gva_t)sched_poll.ports, ports,
                                sched_poll.nr_ports * sizeof(*ports), &e)) {
                *r = -EFAULT;
                return true;
        }

        for (i = 0; i < sched_poll.nr_ports; i++) {
                if (ports[i] >= max_evtchn_port(vcpu->kvm)) {
                        *r = -EINVAL;
                        goto out;
                }
        }

        if (sched_poll.nr_ports == 1)
                vcpu->arch.xen.poll_evtchn = port;
        else
                vcpu->arch.xen.poll_evtchn = -1;

        set_bit(vcpu->vcpu_idx, vcpu->kvm->arch.xen.poll_mask);

        if (!wait_pending_event(vcpu, sched_poll.nr_ports, ports)) {
                vcpu->arch.mp_state = KVM_MP_STATE_HALTED;

                if (sched_poll.timeout)
                        mod_timer(&vcpu->arch.xen.poll_timer,
                                  jiffies + nsecs_to_jiffies(sched_poll.timeout));

                kvm_vcpu_halt(vcpu);

                if (sched_poll.timeout)
                        del_timer(&vcpu->arch.xen.poll_timer);

                vcpu->arch.mp_state = KVM_MP_STATE_RUNNABLE;
        }

        vcpu->arch.xen.poll_evtchn = 0;
        *r = 0;
out:
        /* Really, this is only needed in case of timeout */
        clear_bit(vcpu->vcpu_idx, vcpu->kvm->arch.xen.poll_mask);

        if (unlikely(sched_poll.nr_ports > 1))
                kfree(ports);
        return true;
}

static void cancel_evtchn_poll(struct timer_list *t)
{
        struct kvm_vcpu *vcpu = from_timer(vcpu, t, arch.xen.poll_timer);

        kvm_make_request(KVM_REQ_UNBLOCK, vcpu);
        kvm_vcpu_kick(vcpu);
}

static bool kvm_xen_hcall_sched_op(struct kvm_vcpu *vcpu, bool longmode,
                                   int cmd, u64 param, u64 *r)
{
        switch (cmd) {
        case SCHEDOP_poll:
                if (kvm_xen_schedop_poll(vcpu, longmode, param, r))
                        return true;
                fallthrough;
        case SCHEDOP_yield:
                kvm_vcpu_on_spin(vcpu, true);
                *r = 0;
                return true;
        default:
                break;
        }

        return false;
}

struct compat_vcpu_set_singleshot_timer {
    uint64_t timeout_abs_ns;
    uint32_t flags;
} __attribute__((packed));

static bool kvm_xen_hcall_vcpu_op(struct kvm_vcpu *vcpu, bool longmode, int cmd,
                                  int vcpu_id, u64 param, u64 *r)
{
        struct vcpu_set_singleshot_timer oneshot;
        struct x86_exception e;

        if (!kvm_xen_timer_enabled(vcpu))
                return false;

        switch (cmd) {
        case VCPUOP_set_singleshot_timer:
                if (vcpu->arch.xen.vcpu_id != vcpu_id) {
                        *r = -EINVAL;
                        return true;
                }

                /*
                 * The only difference for 32-bit compat is the 4 bytes of
                 * padding after the interesting part of the structure. So
                 * for a faithful emulation of Xen we have to *try* to copy
                 * the padding and return -EFAULT if we can't. Otherwise we
                 * might as well just have copied the 12-byte 32-bit struct.
                 */
                BUILD_BUG_ON(offsetof(struct compat_vcpu_set_singleshot_timer, timeout_abs_ns) !=
                             offsetof(struct vcpu_set_singleshot_timer, timeout_abs_ns));
                BUILD_BUG_ON(sizeof_field(struct compat_vcpu_set_singleshot_timer, timeout_abs_ns) !=
                             sizeof_field(struct vcpu_set_singleshot_timer, timeout_abs_ns));
                BUILD_BUG_ON(offsetof(struct compat_vcpu_set_singleshot_timer, flags) !=
                             offsetof(struct vcpu_set_singleshot_timer, flags));
                BUILD_BUG_ON(sizeof_field(struct compat_vcpu_set_singleshot_timer, flags) !=
                             sizeof_field(struct vcpu_set_singleshot_timer, flags));

                if (kvm_read_guest_virt(vcpu, param, &oneshot, longmode ? sizeof(oneshot) :
                                        sizeof(struct compat_vcpu_set_singleshot_timer), &e)) {
                        *r = -EFAULT;
                        return true;
                }

                kvm_xen_start_timer(vcpu, oneshot.timeout_abs_ns, false);
                *r = 0;
                return true;

        case VCPUOP_stop_singleshot_timer:
                if (vcpu->arch.xen.vcpu_id != vcpu_id) {
                        *r = -EINVAL;
                        return true;
                }
                kvm_xen_stop_timer(vcpu);
                *r = 0;
                return true;
        }

        return false;
}

static bool kvm_xen_hcall_set_timer_op(struct kvm_vcpu *vcpu, uint64_t timeout,
                                       u64 *r)
{
        if (!kvm_xen_timer_enabled(vcpu))
                return false;

        if (timeout)
                kvm_xen_start_timer(vcpu, timeout, true);
        else
                kvm_xen_stop_timer(vcpu);

        *r = 0;
        return true;
}

int kvm_xen_hypercall(struct kvm_vcpu *vcpu)
{
        bool longmode;
        u64 input, params[6], r = -ENOSYS;
        bool handled = false;
        u8 cpl;

        input = (u64)kvm_register_read(vcpu, VCPU_REGS_RAX);

        /* Hyper-V hypercalls get bit 31 set in EAX */
        if ((input & 0x80000000) &&
            kvm_hv_hypercall_enabled(vcpu))
                return kvm_hv_hypercall(vcpu);

        longmode = is_64_bit_hypercall(vcpu);
        if (!longmode) {
                params[0] = (u32)kvm_rbx_read(vcpu);
                params[1] = (u32)kvm_rcx_read(vcpu);
                params[2] = (u32)kvm_rdx_read(vcpu);
                params[3] = (u32)kvm_rsi_read(vcpu);
                params[4] = (u32)kvm_rdi_read(vcpu);
                params[5] = (u32)kvm_rbp_read(vcpu);
        }
#ifdef CONFIG_X86_64
        else {
                params[0] = (u64)kvm_rdi_read(vcpu);
                params[1] = (u64)kvm_rsi_read(vcpu);
                params[2] = (u64)kvm_rdx_read(vcpu);
                params[3] = (u64)kvm_r10_read(vcpu);
                params[4] = (u64)kvm_r8_read(vcpu);
                params[5] = (u64)kvm_r9_read(vcpu);
        }
#endif
        cpl = kvm_x86_call(get_cpl)(vcpu);
        trace_kvm_xen_hypercall(cpl, input, params[0], params[1], params[2],
                                params[3], params[4], params[5]);

        /*
         * Only allow hypercall acceleration for CPL0. The rare hypercalls that
         * are permitted in guest userspace can be handled by the VMM.
         */
        if (unlikely(cpl > 0))
                goto handle_in_userspace;

        switch (input) {
        case __HYPERVISOR_xen_version:
                if (params[0] == XENVER_version && vcpu->kvm->arch.xen.xen_version) {
                        r = vcpu->kvm->arch.xen.xen_version;
                        handled = true;
                }
                break;
        case __HYPERVISOR_event_channel_op:
                if (params[0] == EVTCHNOP_send)
                        handled = kvm_xen_hcall_evtchn_send(vcpu, params[1], &r);
                break;
        case __HYPERVISOR_sched_op:
                handled = kvm_xen_hcall_sched_op(vcpu, longmode, params[0],
                                                 params[1], &r);
                break;
        case __HYPERVISOR_vcpu_op:
                handled = kvm_xen_hcall_vcpu_op(vcpu, longmode, params[0], params[1],
                                                params[2], &r);
                break;
        case __HYPERVISOR_set_timer_op: {
                u64 timeout = params[0];
                /* In 32-bit mode, the 64-bit timeout is in two 32-bit params. */
                if (!longmode)
                        timeout |= params[1] << 32;
                handled = kvm_xen_hcall_set_timer_op(vcpu, timeout, &r);
                break;
        }
        default:
                break;
        }

        if (handled)
                return kvm_xen_hypercall_set_result(vcpu, r);

handle_in_userspace:
        vcpu->run->exit_reason = KVM_EXIT_XEN;
        vcpu->run->xen.type = KVM_EXIT_XEN_HCALL;
        vcpu->run->xen.u.hcall.longmode = longmode;
        vcpu->run->xen.u.hcall.cpl = cpl;
        vcpu->run->xen.u.hcall.input = input;
        vcpu->run->xen.u.hcall.params[0] = params[0];
        vcpu->run->xen.u.hcall.params[1] = params[1];
        vcpu->run->xen.u.hcall.params[2] = params[2];
        vcpu->run->xen.u.hcall.params[3] = params[3];
        vcpu->run->xen.u.hcall.params[4] = params[4];
        vcpu->run->xen.u.hcall.params[5] = params[5];
        vcpu->arch.xen.hypercall_rip = kvm_get_linear_rip(vcpu);
        vcpu->arch.complete_userspace_io =
                kvm_xen_hypercall_complete_userspace;

        return 0;
}

static void kvm_xen_check_poller(struct kvm_vcpu *vcpu, int port)
{
        int poll_evtchn = vcpu->arch.xen.poll_evtchn;

        if ((poll_evtchn == port || poll_evtchn == -1) &&
            test_and_clear_bit(vcpu->vcpu_idx, vcpu->kvm->arch.xen.poll_mask)) {
                kvm_make_request(KVM_REQ_UNBLOCK, vcpu);
                kvm_vcpu_kick(vcpu);
        }
}

/*
 * The return value from this function is propagated to kvm_set_irq() API,
 * so it returns:
 *  < 0   Interrupt was ignored (masked or not delivered for other reasons)
 *  = 0   Interrupt was coalesced (previous irq is still pending)
 *  > 0   Number of CPUs interrupt was delivered to
 *
 * It is also called directly from kvm_arch_set_irq_inatomic(), where the
 * only check on its return value is a comparison with -EWOULDBLOCK'.
 */
int kvm_xen_set_evtchn_fast(struct kvm_xen_evtchn *xe, struct kvm *kvm)
{
        struct gfn_to_pfn_cache *gpc = &kvm->arch.xen.shinfo_cache;
        struct kvm_vcpu *vcpu;
        unsigned long *pending_bits, *mask_bits;
        unsigned long flags;
        int port_word_bit;
        bool kick_vcpu = false;
        int vcpu_idx, idx, rc;

        vcpu_idx = READ_ONCE(xe->vcpu_idx);
        if (vcpu_idx >= 0)
                vcpu = kvm_get_vcpu(kvm, vcpu_idx);
        else {
                vcpu = kvm_get_vcpu_by_id(kvm, xe->vcpu_id);
                if (!vcpu)
                        return -EINVAL;
                WRITE_ONCE(xe->vcpu_idx, vcpu->vcpu_idx);
        }

        if (xe->port >= max_evtchn_port(kvm))
                return -EINVAL;

        rc = -EWOULDBLOCK;

        idx = srcu_read_lock(&kvm->srcu);

        read_lock_irqsave(&gpc->lock, flags);
        if (!kvm_gpc_check(gpc, PAGE_SIZE))
                goto out_rcu;

        if (IS_ENABLED(CONFIG_64BIT) && kvm->arch.xen.long_mode) {
                struct shared_info *shinfo = gpc->khva;
                pending_bits = (unsigned long *)&shinfo->evtchn_pending;
                mask_bits = (unsigned long *)&shinfo->evtchn_mask;
                port_word_bit = xe->port / 64;
        } else {
                struct compat_shared_info *shinfo = gpc->khva;
                pending_bits = (unsigned long *)&shinfo->evtchn_pending;
                mask_bits = (unsigned long *)&shinfo->evtchn_mask;
                port_word_bit = xe->port / 32;
        }

        /*
         * If this port wasn't already set, and if it isn't masked, then
         * we try to set the corresponding bit in the in-kernel shadow of
         * evtchn_pending_sel for the target vCPU. And if *that* wasn't
         * already set, then we kick the vCPU in question to write to the
         * *real* evtchn_pending_sel in its own guest vcpu_info struct.
         */
        if (test_and_set_bit(xe->port, pending_bits)) {
                rc = 0; /* It was already raised */
        } else if (test_bit(xe->port, mask_bits)) {
                rc = -ENOTCONN; /* Masked */
                kvm_xen_check_poller(vcpu, xe->port);
        } else {
                rc = 1; /* Delivered to the bitmap in shared_info. */
                /* Now switch to the vCPU's vcpu_info to set the index and pending_sel */
                read_unlock_irqrestore(&gpc->lock, flags);
                gpc = &vcpu->arch.xen.vcpu_info_cache;

                read_lock_irqsave(&gpc->lock, flags);
                if (!kvm_gpc_check(gpc, sizeof(struct vcpu_info))) {
                        /*
                         * Could not access the vcpu_info. Set the bit in-kernel
                         * and prod the vCPU to deliver it for itself.
                         */
                        if (!test_and_set_bit(port_word_bit, &vcpu->arch.xen.evtchn_pending_sel))
                                kick_vcpu = true;
                        goto out_rcu;
                }

                if (IS_ENABLED(CONFIG_64BIT) && kvm->arch.xen.long_mode) {
                        struct vcpu_info *vcpu_info = gpc->khva;
                        if (!test_and_set_bit(port_word_bit, &vcpu_info->evtchn_pending_sel)) {
                                WRITE_ONCE(vcpu_info->evtchn_upcall_pending, 1);
                                kick_vcpu = true;
                        }
                } else {
                        struct compat_vcpu_info *vcpu_info = gpc->khva;
                        if (!test_and_set_bit(port_word_bit,
                                              (unsigned long *)&vcpu_info->evtchn_pending_sel)) {
                                WRITE_ONCE(vcpu_info->evtchn_upcall_pending, 1);
                                kick_vcpu = true;
                        }
                }

                /* For the per-vCPU lapic vector, deliver it as MSI. */
                if (kick_vcpu && vcpu->arch.xen.upcall_vector) {
                        kvm_xen_inject_vcpu_vector(vcpu);
                        kick_vcpu = false;
                }
        }

 out_rcu:
        read_unlock_irqrestore(&gpc->lock, flags);
        srcu_read_unlock(&kvm->srcu, idx);

        if (kick_vcpu) {
                kvm_make_request(KVM_REQ_UNBLOCK, vcpu);
                kvm_vcpu_kick(vcpu);
        }

        return rc;
}

static int kvm_xen_set_evtchn(struct kvm_xen_evtchn *xe, struct kvm *kvm)
{
        bool mm_borrowed = false;
        int rc;

        rc = kvm_xen_set_evtchn_fast(xe, kvm);
        if (rc != -EWOULDBLOCK)
                return rc;

        if (current->mm != kvm->mm) {
                /*
                 * If not on a thread which already belongs to this KVM,
                 * we'd better be in the irqfd workqueue.
                 */
                if (WARN_ON_ONCE(current->mm))
                        return -EINVAL;

                kthread_use_mm(kvm->mm);
                mm_borrowed = true;
        }

        /*
         * It is theoretically possible for the page to be unmapped
         * and the MMU notifier to invalidate the shared_info before
         * we even get to use it. In that case, this looks like an
         * infinite loop. It was tempting to do it via the userspace
         * HVA instead... but that just *hides* the fact that it's
         * an infinite loop, because if a fault occurs and it waits
         * for the page to come back, it can *still* immediately
         * fault and have to wait again, repeatedly.
         *
         * Conversely, the page could also have been reinstated by
         * another thread before we even obtain the mutex above, so
         * check again *first* before remapping it.
         */
        do {
                struct gfn_to_pfn_cache *gpc = &kvm->arch.xen.shinfo_cache;
                int idx;

                rc = kvm_xen_set_evtchn_fast(xe, kvm);
                if (rc != -EWOULDBLOCK)
                        break;

                idx = srcu_read_lock(&kvm->srcu);
                rc = kvm_gpc_refresh(gpc, PAGE_SIZE);
                srcu_read_unlock(&kvm->srcu, idx);
        } while(!rc);

        if (mm_borrowed)
                kthread_unuse_mm(kvm->mm);

        return rc;
}

/* This is the version called from kvm_set_irq() as the .set function */
static int evtchn_set_fn(struct kvm_kernel_irq_routing_entry *e, struct kvm *kvm,
                         int irq_source_id, int level, bool line_status)
{
        if (!level)
                return -EINVAL;

        return kvm_xen_set_evtchn(&e->xen_evtchn, kvm);
}

/*
 * Set up an event channel interrupt from the KVM IRQ routing table.
 * Used for e.g. PIRQ from passed through physical devices.
 */
int kvm_xen_setup_evtchn(struct kvm *kvm,
                         struct kvm_kernel_irq_routing_entry *e,
                         const struct kvm_irq_routing_entry *ue)

{
        struct kvm_vcpu *vcpu;

        if (ue->u.xen_evtchn.port >= max_evtchn_port(kvm))
                return -EINVAL;

        /* We only support 2 level event channels for now */
        if (ue->u.xen_evtchn.priority != KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL)
                return -EINVAL;

        /*
         * Xen gives us interesting mappings from vCPU index to APIC ID,
         * which means kvm_get_vcpu_by_id() has to iterate over all vCPUs
         * to find it. Do that once at setup time, instead of every time.
         * But beware that on live update / live migration, the routing
         * table might be reinstated before the vCPU threads have finished
         * recreating their vCPUs.
         */
        vcpu = kvm_get_vcpu_by_id(kvm, ue->u.xen_evtchn.vcpu);
        if (vcpu)
                e->xen_evtchn.vcpu_idx = vcpu->vcpu_idx;
        else
                e->xen_evtchn.vcpu_idx = -1;

        e->xen_evtchn.port = ue->u.xen_evtchn.port;
        e->xen_evtchn.vcpu_id = ue->u.xen_evtchn.vcpu;
        e->xen_evtchn.priority = ue->u.xen_evtchn.priority;
        e->set = evtchn_set_fn;

        return 0;
}

/*
 * Explicit event sending from userspace with KVM_XEN_HVM_EVTCHN_SEND ioctl.
 */
int kvm_xen_hvm_evtchn_send(struct kvm *kvm, struct kvm_irq_routing_xen_evtchn *uxe)
{
        struct kvm_xen_evtchn e;
        int ret;

        if (!uxe->port || uxe->port >= max_evtchn_port(kvm))
                return -EINVAL;

        /* We only support 2 level event channels for now */
        if (uxe->priority != KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL)
                return -EINVAL;

        e.port = uxe->port;
        e.vcpu_id = uxe->vcpu;
        e.vcpu_idx = -1;
        e.priority = uxe->priority;

        ret = kvm_xen_set_evtchn(&e, kvm);

        /*
         * None of that 'return 1 if it actually got delivered' nonsense.
         * We don't care if it was masked (-ENOTCONN) either.
         */
        if (ret > 0 || ret == -ENOTCONN)
                ret = 0;

        return ret;
}

/*
 * Support for *outbound* event channel events via the EVTCHNOP_send hypercall.
 */
struct evtchnfd {
        u32 send_port;
        u32 type;
        union {
                struct kvm_xen_evtchn port;
                struct {
                        u32 port; /* zero */
                        struct eventfd_ctx *ctx;
                } eventfd;
        } deliver;
};

/*
 * Update target vCPU or priority for a registered sending channel.
 */
static int kvm_xen_eventfd_update(struct kvm *kvm,
                                  struct kvm_xen_hvm_attr *data)
{
        u32 port = data->u.evtchn.send_port;
        struct evtchnfd *evtchnfd;
        int ret;

        /* Protect writes to evtchnfd as well as the idr lookup.  */
        mutex_lock(&kvm->arch.xen.xen_lock);
        evtchnfd = idr_find(&kvm->arch.xen.evtchn_ports, port);

        ret = -ENOENT;
        if (!evtchnfd)
                goto out_unlock;

        /* For an UPDATE, nothing may change except the priority/vcpu */
        ret = -EINVAL;
        if (evtchnfd->type != data->u.evtchn.type)
                goto out_unlock;

        /*
         * Port cannot change, and if it's zero that was an eventfd
         * which can't be changed either.
         */
        if (!evtchnfd->deliver.port.port ||
            evtchnfd->deliver.port.port != data->u.evtchn.deliver.port.port)
                goto out_unlock;

        /* We only support 2 level event channels for now */
        if (data->u.evtchn.deliver.port.priority != KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL)
                goto out_unlock;

        evtchnfd->deliver.port.priority = data->u.evtchn.deliver.port.priority;
        if (evtchnfd->deliver.port.vcpu_id != data->u.evtchn.deliver.port.vcpu) {
                evtchnfd->deliver.port.vcpu_id = data->u.evtchn.deliver.port.vcpu;
                evtchnfd->deliver.port.vcpu_idx = -1;
        }
        ret = 0;
out_unlock:
        mutex_unlock(&kvm->arch.xen.xen_lock);
        return ret;
}

/*
 * Configure the target (eventfd or local port delivery) for sending on
 * a given event channel.
 */
static int kvm_xen_eventfd_assign(struct kvm *kvm,
                                  struct kvm_xen_hvm_attr *data)
{
        u32 port = data->u.evtchn.send_port;
        struct eventfd_ctx *eventfd = NULL;
        struct evtchnfd *evtchnfd;
        int ret = -EINVAL;

        evtchnfd = kzalloc(sizeof(struct evtchnfd), GFP_KERNEL);
        if (!evtchnfd)
                return -ENOMEM;

        switch(data->u.evtchn.type) {
        case EVTCHNSTAT_ipi:
                /* IPI  must map back to the same port# */
                if (data->u.evtchn.deliver.port.port != data->u.evtchn.send_port)
                        goto out_noeventfd; /* -EINVAL */
                break;

        case EVTCHNSTAT_interdomain:
                if (data->u.evtchn.deliver.port.port) {
                        if (data->u.evtchn.deliver.port.port >= max_evtchn_port(kvm))
                                goto out_noeventfd; /* -EINVAL */
                } else {
                        eventfd = eventfd_ctx_fdget(data->u.evtchn.deliver.eventfd.fd);
                        if (IS_ERR(eventfd)) {
                                ret = PTR_ERR(eventfd);
                                goto out_noeventfd;
                        }
                }
                break;

        case EVTCHNSTAT_virq:
        case EVTCHNSTAT_closed:
        case EVTCHNSTAT_unbound:
        case EVTCHNSTAT_pirq:
        default: /* Unknown event channel type */
                goto out; /* -EINVAL */
        }

        evtchnfd->send_port = data->u.evtchn.send_port;
        evtchnfd->type = data->u.evtchn.type;
        if (eventfd) {
                evtchnfd->deliver.eventfd.ctx = eventfd;
        } else {
                /* We only support 2 level event channels for now */
                if (data->u.evtchn.deliver.port.priority != KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL)
                        goto out; /* -EINVAL; */

                evtchnfd->deliver.port.port = data->u.evtchn.deliver.port.port;
                evtchnfd->deliver.port.vcpu_id = data->u.evtchn.deliver.port.vcpu;
                evtchnfd->deliver.port.vcpu_idx = -1;
                evtchnfd->deliver.port.priority = data->u.evtchn.deliver.port.priority;
        }

        mutex_lock(&kvm->arch.xen.xen_lock);
        ret = idr_alloc(&kvm->arch.xen.evtchn_ports, evtchnfd, port, port + 1,
                        GFP_KERNEL);
        mutex_unlock(&kvm->arch.xen.xen_lock);
        if (ret >= 0)
                return 0;

        if (ret == -ENOSPC)
                ret = -EEXIST;
out:
        if (eventfd)
                eventfd_ctx_put(eventfd);
out_noeventfd:
        kfree(evtchnfd);
        return ret;
}

static int kvm_xen_eventfd_deassign(struct kvm *kvm, u32 port)
{
        struct evtchnfd *evtchnfd;

        mutex_lock(&kvm->arch.xen.xen_lock);
        evtchnfd = idr_remove(&kvm->arch.xen.evtchn_ports, port);
        mutex_unlock(&kvm->arch.xen.xen_lock);

        if (!evtchnfd)
                return -ENOENT;

        synchronize_srcu(&kvm->srcu);
        if (!evtchnfd->deliver.port.port)
                eventfd_ctx_put(evtchnfd->deliver.eventfd.ctx);
        kfree(evtchnfd);
        return 0;
}

static int kvm_xen_eventfd_reset(struct kvm *kvm)
{
        struct evtchnfd *evtchnfd, **all_evtchnfds;
        int i;
        int n = 0;

        mutex_lock(&kvm->arch.xen.xen_lock);

        /*
         * Because synchronize_srcu() cannot be called inside the
         * critical section, first collect all the evtchnfd objects
         * in an array as they are removed from evtchn_ports.
         */
        idr_for_each_entry(&kvm->arch.xen.evtchn_ports, evtchnfd, i)
                n++;

        all_evtchnfds = kmalloc_array(n, sizeof(struct evtchnfd *), GFP_KERNEL);
        if (!all_evtchnfds) {
                mutex_unlock(&kvm->arch.xen.xen_lock);
                return -ENOMEM;
        }

        n = 0;
        idr_for_each_entry(&kvm->arch.xen.evtchn_ports, evtchnfd, i) {
                all_evtchnfds[n++] = evtchnfd;
                idr_remove(&kvm->arch.xen.evtchn_ports, evtchnfd->send_port);
        }
        mutex_unlock(&kvm->arch.xen.xen_lock);

        synchronize_srcu(&kvm->srcu);

        while (n--) {
                evtchnfd = all_evtchnfds[n];
                if (!evtchnfd->deliver.port.port)
                        eventfd_ctx_put(evtchnfd->deliver.eventfd.ctx);
                kfree(evtchnfd);
        }
        kfree(all_evtchnfds);

        return 0;
}

static int kvm_xen_setattr_evtchn(struct kvm *kvm, struct kvm_xen_hvm_attr *data)
{
        u32 port = data->u.evtchn.send_port;

        if (data->u.evtchn.flags == KVM_XEN_EVTCHN_RESET)
                return kvm_xen_eventfd_reset(kvm);

        if (!port || port >= max_evtchn_port(kvm))
                return -EINVAL;

        if (data->u.evtchn.flags == KVM_XEN_EVTCHN_DEASSIGN)
                return kvm_xen_eventfd_deassign(kvm, port);
        if (data->u.evtchn.flags == KVM_XEN_EVTCHN_UPDATE)
                return kvm_xen_eventfd_update(kvm, data);
        if (data->u.evtchn.flags)
                return -EINVAL;

        return kvm_xen_eventfd_assign(kvm, data);
}

static bool kvm_xen_hcall_evtchn_send(struct kvm_vcpu *vcpu, u64 param, u64 *r)
{
        struct evtchnfd *evtchnfd;
        struct evtchn_send send;
        struct x86_exception e;

        /* Sanity check: this structure is the same for 32-bit and 64-bit */
        BUILD_BUG_ON(sizeof(send) != 4);
        if (kvm_read_guest_virt(vcpu, param, &send, sizeof(send), &e)) {
                *r = -EFAULT;
                return true;
        }

        /*
         * evtchnfd is protected by kvm->srcu; the idr lookup instead
         * is protected by RCU.
         */
        rcu_read_lock();
        evtchnfd = idr_find(&vcpu->kvm->arch.xen.evtchn_ports, send.port);
        rcu_read_unlock();
        if (!evtchnfd)
                return false;

        if (evtchnfd->deliver.port.port) {
                int ret = kvm_xen_set_evtchn(&evtchnfd->deliver.port, vcpu->kvm);
                if (ret < 0 && ret != -ENOTCONN)
                        return false;
        } else {
                eventfd_signal(evtchnfd->deliver.eventfd.ctx);
        }

        *r = 0;
        return true;
}

void kvm_xen_init_vcpu(struct kvm_vcpu *vcpu)
{
        vcpu->arch.xen.vcpu_id = vcpu->vcpu_idx;
        vcpu->arch.xen.poll_evtchn = 0;

        timer_setup(&vcpu->arch.xen.poll_timer, cancel_evtchn_poll, 0);
        hrtimer_init(&vcpu->arch.xen.timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_HARD);
        vcpu->arch.xen.timer.function = xen_timer_callback;

        kvm_gpc_init(&vcpu->arch.xen.runstate_cache, vcpu->kvm);
        kvm_gpc_init(&vcpu->arch.xen.runstate2_cache, vcpu->kvm);
        kvm_gpc_init(&vcpu->arch.xen.vcpu_info_cache, vcpu->kvm);
        kvm_gpc_init(&vcpu->arch.xen.vcpu_time_info_cache, vcpu->kvm);
}

void kvm_xen_destroy_vcpu(struct kvm_vcpu *vcpu)
{
        if (kvm_xen_timer_enabled(vcpu))
                kvm_xen_stop_timer(vcpu);

        kvm_gpc_deactivate(&vcpu->arch.xen.runstate_cache);
        kvm_gpc_deactivate(&vcpu->arch.xen.runstate2_cache);
        kvm_gpc_deactivate(&vcpu->arch.xen.vcpu_info_cache);
        kvm_gpc_deactivate(&vcpu->arch.xen.vcpu_time_info_cache);

        del_timer_sync(&vcpu->arch.xen.poll_timer);
}

void kvm_xen_update_tsc_info(struct kvm_vcpu *vcpu)
{
        struct kvm_cpuid_entry2 *entry;
        u32 function;

        if (!vcpu->arch.xen.cpuid.base)
                return;

        function = vcpu->arch.xen.cpuid.base | XEN_CPUID_LEAF(3);
        if (function > vcpu->arch.xen.cpuid.limit)
                return;

        entry = kvm_find_cpuid_entry_index(vcpu, function, 1);
        if (entry) {
                entry->ecx = vcpu->arch.hv_clock.tsc_to_system_mul;
                entry->edx = vcpu->arch.hv_clock.tsc_shift;
        }

        entry = kvm_find_cpuid_entry_index(vcpu, function, 2);
        if (entry)
                entry->eax = vcpu->arch.hw_tsc_khz;
}

void kvm_xen_init_vm(struct kvm *kvm)
{
        mutex_init(&kvm->arch.xen.xen_lock);
        idr_init(&kvm->arch.xen.evtchn_ports);
        kvm_gpc_init(&kvm->arch.xen.shinfo_cache, kvm);
}

void kvm_xen_destroy_vm(struct kvm *kvm)
{
        struct evtchnfd *evtchnfd;
        int i;

        kvm_gpc_deactivate(&kvm->arch.xen.shinfo_cache);

        idr_for_each_entry(&kvm->arch.xen.evtchn_ports, evtchnfd, i) {
                if (!evtchnfd->deliver.port.port)
                        eventfd_ctx_put(evtchnfd->deliver.eventfd.ctx);
                kfree(evtchnfd);
        }
        idr_destroy(&kvm->arch.xen.evtchn_ports);

        if (kvm->arch.xen_hvm_config.msr)
                static_branch_slow_dec_deferred(&kvm_xen_enabled);
}