KVM: x86/mmu: Remove MMU auditing

[linux.git] / arch / x86 / kernel / sev.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * AMD Memory Encryption Support
 *
 * Copyright (C) 2019 SUSE
 *
 * Author: Joerg Roedel <[email protected]>
 */

#define pr_fmt(fmt)     "SEV: " fmt

#include <linux/sched/debug.h>  /* For show_regs() */
#include <linux/percpu-defs.h>
#include <linux/cc_platform.h>
#include <linux/printk.h>
#include <linux/mm_types.h>
#include <linux/set_memory.h>
#include <linux/memblock.h>
#include <linux/kernel.h>
#include <linux/mm.h>

#include <asm/cpu_entry_area.h>
#include <asm/stacktrace.h>
#include <asm/sev.h>
#include <asm/insn-eval.h>
#include <asm/fpu/xcr.h>
#include <asm/processor.h>
#include <asm/realmode.h>
#include <asm/setup.h>
#include <asm/traps.h>
#include <asm/svm.h>
#include <asm/smp.h>
#include <asm/cpu.h>

#define DR7_RESET_VALUE        0x400

/* For early boot hypervisor communication in SEV-ES enabled guests */
static struct ghcb boot_ghcb_page __bss_decrypted __aligned(PAGE_SIZE);

/*
 * Needs to be in the .data section because we need it NULL before bss is
 * cleared
 */
static struct ghcb __initdata *boot_ghcb;

/* #VC handler runtime per-CPU data */
struct sev_es_runtime_data {
        struct ghcb ghcb_page;

        /*
         * Reserve one page per CPU as backup storage for the unencrypted GHCB.
         * It is needed when an NMI happens while the #VC handler uses the real
         * GHCB, and the NMI handler itself is causing another #VC exception. In
         * that case the GHCB content of the first handler needs to be backed up
         * and restored.
         */
        struct ghcb backup_ghcb;

        /*
         * Mark the per-cpu GHCBs as in-use to detect nested #VC exceptions.
         * There is no need for it to be atomic, because nothing is written to
         * the GHCB between the read and the write of ghcb_active. So it is safe
         * to use it when a nested #VC exception happens before the write.
         *
         * This is necessary for example in the #VC->NMI->#VC case when the NMI
         * happens while the first #VC handler uses the GHCB. When the NMI code
         * raises a second #VC handler it might overwrite the contents of the
         * GHCB written by the first handler. To avoid this the content of the
         * GHCB is saved and restored when the GHCB is detected to be in use
         * already.
         */
        bool ghcb_active;
        bool backup_ghcb_active;

        /*
         * Cached DR7 value - write it on DR7 writes and return it on reads.
         * That value will never make it to the real hardware DR7 as debugging
         * is currently unsupported in SEV-ES guests.
         */
        unsigned long dr7;
};

struct ghcb_state {
        struct ghcb *ghcb;
};

static DEFINE_PER_CPU(struct sev_es_runtime_data*, runtime_data);
DEFINE_STATIC_KEY_FALSE(sev_es_enable_key);

static __always_inline bool on_vc_stack(struct pt_regs *regs)
{
        unsigned long sp = regs->sp;

        /* User-mode RSP is not trusted */
        if (user_mode(regs))
                return false;

        /* SYSCALL gap still has user-mode RSP */
        if (ip_within_syscall_gap(regs))
                return false;

        return ((sp >= __this_cpu_ist_bottom_va(VC)) && (sp < __this_cpu_ist_top_va(VC)));
}

/*
 * This function handles the case when an NMI is raised in the #VC
 * exception handler entry code, before the #VC handler has switched off
 * its IST stack. In this case, the IST entry for #VC must be adjusted,
 * so that any nested #VC exception will not overwrite the stack
 * contents of the interrupted #VC handler.
 *
 * The IST entry is adjusted unconditionally so that it can be also be
 * unconditionally adjusted back in __sev_es_ist_exit(). Otherwise a
 * nested sev_es_ist_exit() call may adjust back the IST entry too
 * early.
 *
 * The __sev_es_ist_enter() and __sev_es_ist_exit() functions always run
 * on the NMI IST stack, as they are only called from NMI handling code
 * right now.
 */
void noinstr __sev_es_ist_enter(struct pt_regs *regs)
{
        unsigned long old_ist, new_ist;

        /* Read old IST entry */
        new_ist = old_ist = __this_cpu_read(cpu_tss_rw.x86_tss.ist[IST_INDEX_VC]);

        /*
         * If NMI happened while on the #VC IST stack, set the new IST
         * value below regs->sp, so that the interrupted stack frame is
         * not overwritten by subsequent #VC exceptions.
         */
        if (on_vc_stack(regs))
                new_ist = regs->sp;

        /*
         * Reserve additional 8 bytes and store old IST value so this
         * adjustment can be unrolled in __sev_es_ist_exit().
         */
        new_ist -= sizeof(old_ist);
        *(unsigned long *)new_ist = old_ist;

        /* Set new IST entry */
        this_cpu_write(cpu_tss_rw.x86_tss.ist[IST_INDEX_VC], new_ist);
}

void noinstr __sev_es_ist_exit(void)
{
        unsigned long ist;

        /* Read IST entry */
        ist = __this_cpu_read(cpu_tss_rw.x86_tss.ist[IST_INDEX_VC]);

        if (WARN_ON(ist == __this_cpu_ist_top_va(VC)))
                return;

        /* Read back old IST entry and write it to the TSS */
        this_cpu_write(cpu_tss_rw.x86_tss.ist[IST_INDEX_VC], *(unsigned long *)ist);
}

/*
 * Nothing shall interrupt this code path while holding the per-CPU
 * GHCB. The backup GHCB is only for NMIs interrupting this path.
 *
 * Callers must disable local interrupts around it.
 */
static noinstr struct ghcb *__sev_get_ghcb(struct ghcb_state *state)
{
        struct sev_es_runtime_data *data;
        struct ghcb *ghcb;

        WARN_ON(!irqs_disabled());

        data = this_cpu_read(runtime_data);
        ghcb = &data->ghcb_page;

        if (unlikely(data->ghcb_active)) {
                /* GHCB is already in use - save its contents */

                if (unlikely(data->backup_ghcb_active)) {
                        /*
                         * Backup-GHCB is also already in use. There is no way
                         * to continue here so just kill the machine. To make
                         * panic() work, mark GHCBs inactive so that messages
                         * can be printed out.
                         */
                        data->ghcb_active        = false;
                        data->backup_ghcb_active = false;

                        instrumentation_begin();
                        panic("Unable to handle #VC exception! GHCB and Backup GHCB are already in use");
                        instrumentation_end();
                }

                /* Mark backup_ghcb active before writing to it */
                data->backup_ghcb_active = true;

                state->ghcb = &data->backup_ghcb;

                /* Backup GHCB content */
                *state->ghcb = *ghcb;
        } else {
                state->ghcb = NULL;
                data->ghcb_active = true;
        }

        return ghcb;
}

static inline u64 sev_es_rd_ghcb_msr(void)
{
        return __rdmsr(MSR_AMD64_SEV_ES_GHCB);
}

static __always_inline void sev_es_wr_ghcb_msr(u64 val)
{
        u32 low, high;

        low  = (u32)(val);
        high = (u32)(val >> 32);

        native_wrmsr(MSR_AMD64_SEV_ES_GHCB, low, high);
}

static int vc_fetch_insn_kernel(struct es_em_ctxt *ctxt,
                                unsigned char *buffer)
{
        return copy_from_kernel_nofault(buffer, (unsigned char *)ctxt->regs->ip, MAX_INSN_SIZE);
}

static enum es_result __vc_decode_user_insn(struct es_em_ctxt *ctxt)
{
        char buffer[MAX_INSN_SIZE];
        int insn_bytes;

        insn_bytes = insn_fetch_from_user_inatomic(ctxt->regs, buffer);
        if (insn_bytes == 0) {
                /* Nothing could be copied */
                ctxt->fi.vector     = X86_TRAP_PF;
                ctxt->fi.error_code = X86_PF_INSTR | X86_PF_USER;
                ctxt->fi.cr2        = ctxt->regs->ip;
                return ES_EXCEPTION;
        } else if (insn_bytes == -EINVAL) {
                /* Effective RIP could not be calculated */
                ctxt->fi.vector     = X86_TRAP_GP;
                ctxt->fi.error_code = 0;
                ctxt->fi.cr2        = 0;
                return ES_EXCEPTION;
        }

        if (!insn_decode_from_regs(&ctxt->insn, ctxt->regs, buffer, insn_bytes))
                return ES_DECODE_FAILED;

        if (ctxt->insn.immediate.got)
                return ES_OK;
        else
                return ES_DECODE_FAILED;
}

static enum es_result __vc_decode_kern_insn(struct es_em_ctxt *ctxt)
{
        char buffer[MAX_INSN_SIZE];
        int res, ret;

        res = vc_fetch_insn_kernel(ctxt, buffer);
        if (res) {
                ctxt->fi.vector     = X86_TRAP_PF;
                ctxt->fi.error_code = X86_PF_INSTR;
                ctxt->fi.cr2        = ctxt->regs->ip;
                return ES_EXCEPTION;
        }

        ret = insn_decode(&ctxt->insn, buffer, MAX_INSN_SIZE, INSN_MODE_64);
        if (ret < 0)
                return ES_DECODE_FAILED;
        else
                return ES_OK;
}

static enum es_result vc_decode_insn(struct es_em_ctxt *ctxt)
{
        if (user_mode(ctxt->regs))
                return __vc_decode_user_insn(ctxt);
        else
                return __vc_decode_kern_insn(ctxt);
}

static enum es_result vc_write_mem(struct es_em_ctxt *ctxt,
                                   char *dst, char *buf, size_t size)
{
        unsigned long error_code = X86_PF_PROT | X86_PF_WRITE;

        /*
         * This function uses __put_user() independent of whether kernel or user
         * memory is accessed. This works fine because __put_user() does no
         * sanity checks of the pointer being accessed. All that it does is
         * to report when the access failed.
         *
         * Also, this function runs in atomic context, so __put_user() is not
         * allowed to sleep. The page-fault handler detects that it is running
         * in atomic context and will not try to take mmap_sem and handle the
         * fault, so additional pagefault_enable()/disable() calls are not
         * needed.
         *
         * The access can't be done via copy_to_user() here because
         * vc_write_mem() must not use string instructions to access unsafe
         * memory. The reason is that MOVS is emulated by the #VC handler by
         * splitting the move up into a read and a write and taking a nested #VC
         * exception on whatever of them is the MMIO access. Using string
         * instructions here would cause infinite nesting.
         */
        switch (size) {
        case 1: {
                u8 d1;
                u8 __user *target = (u8 __user *)dst;

                memcpy(&d1, buf, 1);
                if (__put_user(d1, target))
                        goto fault;
                break;
        }
        case 2: {
                u16 d2;
                u16 __user *target = (u16 __user *)dst;

                memcpy(&d2, buf, 2);
                if (__put_user(d2, target))
                        goto fault;
                break;
        }
        case 4: {
                u32 d4;
                u32 __user *target = (u32 __user *)dst;

                memcpy(&d4, buf, 4);
                if (__put_user(d4, target))
                        goto fault;
                break;
        }
        case 8: {
                u64 d8;
                u64 __user *target = (u64 __user *)dst;

                memcpy(&d8, buf, 8);
                if (__put_user(d8, target))
                        goto fault;
                break;
        }
        default:
                WARN_ONCE(1, "%s: Invalid size: %zu\n", __func__, size);
                return ES_UNSUPPORTED;
        }

        return ES_OK;

fault:
        if (user_mode(ctxt->regs))
                error_code |= X86_PF_USER;

        ctxt->fi.vector = X86_TRAP_PF;
        ctxt->fi.error_code = error_code;
        ctxt->fi.cr2 = (unsigned long)dst;

        return ES_EXCEPTION;
}

static enum es_result vc_read_mem(struct es_em_ctxt *ctxt,
                                  char *src, char *buf, size_t size)
{
        unsigned long error_code = X86_PF_PROT;

        /*
         * This function uses __get_user() independent of whether kernel or user
         * memory is accessed. This works fine because __get_user() does no
         * sanity checks of the pointer being accessed. All that it does is
         * to report when the access failed.
         *
         * Also, this function runs in atomic context, so __get_user() is not
         * allowed to sleep. The page-fault handler detects that it is running
         * in atomic context and will not try to take mmap_sem and handle the
         * fault, so additional pagefault_enable()/disable() calls are not
         * needed.
         *
         * The access can't be done via copy_from_user() here because
         * vc_read_mem() must not use string instructions to access unsafe
         * memory. The reason is that MOVS is emulated by the #VC handler by
         * splitting the move up into a read and a write and taking a nested #VC
         * exception on whatever of them is the MMIO access. Using string
         * instructions here would cause infinite nesting.
         */
        switch (size) {
        case 1: {
                u8 d1;
                u8 __user *s = (u8 __user *)src;

                if (__get_user(d1, s))
                        goto fault;
                memcpy(buf, &d1, 1);
                break;
        }
        case 2: {
                u16 d2;
                u16 __user *s = (u16 __user *)src;

                if (__get_user(d2, s))
                        goto fault;
                memcpy(buf, &d2, 2);
                break;
        }
        case 4: {
                u32 d4;
                u32 __user *s = (u32 __user *)src;

                if (__get_user(d4, s))
                        goto fault;
                memcpy(buf, &d4, 4);
                break;
        }
        case 8: {
                u64 d8;
                u64 __user *s = (u64 __user *)src;
                if (__get_user(d8, s))
                        goto fault;
                memcpy(buf, &d8, 8);
                break;
        }
        default:
                WARN_ONCE(1, "%s: Invalid size: %zu\n", __func__, size);
                return ES_UNSUPPORTED;
        }

        return ES_OK;

fault:
        if (user_mode(ctxt->regs))
                error_code |= X86_PF_USER;

        ctxt->fi.vector = X86_TRAP_PF;
        ctxt->fi.error_code = error_code;
        ctxt->fi.cr2 = (unsigned long)src;

        return ES_EXCEPTION;
}

static enum es_result vc_slow_virt_to_phys(struct ghcb *ghcb, struct es_em_ctxt *ctxt,
                                           unsigned long vaddr, phys_addr_t *paddr)
{
        unsigned long va = (unsigned long)vaddr;
        unsigned int level;
        phys_addr_t pa;
        pgd_t *pgd;
        pte_t *pte;

        pgd = __va(read_cr3_pa());
        pgd = &pgd[pgd_index(va)];
        pte = lookup_address_in_pgd(pgd, va, &level);
        if (!pte) {
                ctxt->fi.vector     = X86_TRAP_PF;
                ctxt->fi.cr2        = vaddr;
                ctxt->fi.error_code = 0;

                if (user_mode(ctxt->regs))
                        ctxt->fi.error_code |= X86_PF_USER;

                return ES_EXCEPTION;
        }

        if (WARN_ON_ONCE(pte_val(*pte) & _PAGE_ENC))
                /* Emulated MMIO to/from encrypted memory not supported */
                return ES_UNSUPPORTED;

        pa = (phys_addr_t)pte_pfn(*pte) << PAGE_SHIFT;
        pa |= va & ~page_level_mask(level);

        *paddr = pa;

        return ES_OK;
}

/* Include code shared with pre-decompression boot stage */
#include "sev-shared.c"

static noinstr void __sev_put_ghcb(struct ghcb_state *state)
{
        struct sev_es_runtime_data *data;
        struct ghcb *ghcb;

        WARN_ON(!irqs_disabled());

        data = this_cpu_read(runtime_data);
        ghcb = &data->ghcb_page;

        if (state->ghcb) {
                /* Restore GHCB from Backup */
                *ghcb = *state->ghcb;
                data->backup_ghcb_active = false;
                state->ghcb = NULL;
        } else {
                /*
                 * Invalidate the GHCB so a VMGEXIT instruction issued
                 * from userspace won't appear to be valid.
                 */
                vc_ghcb_invalidate(ghcb);
                data->ghcb_active = false;
        }
}

void noinstr __sev_es_nmi_complete(void)
{
        struct ghcb_state state;
        struct ghcb *ghcb;

        ghcb = __sev_get_ghcb(&state);

        vc_ghcb_invalidate(ghcb);
        ghcb_set_sw_exit_code(ghcb, SVM_VMGEXIT_NMI_COMPLETE);
        ghcb_set_sw_exit_info_1(ghcb, 0);
        ghcb_set_sw_exit_info_2(ghcb, 0);

        sev_es_wr_ghcb_msr(__pa_nodebug(ghcb));
        VMGEXIT();

        __sev_put_ghcb(&state);
}

static u64 get_jump_table_addr(void)
{
        struct ghcb_state state;
        unsigned long flags;
        struct ghcb *ghcb;
        u64 ret = 0;

        local_irq_save(flags);

        ghcb = __sev_get_ghcb(&state);

        vc_ghcb_invalidate(ghcb);
        ghcb_set_sw_exit_code(ghcb, SVM_VMGEXIT_AP_JUMP_TABLE);
        ghcb_set_sw_exit_info_1(ghcb, SVM_VMGEXIT_GET_AP_JUMP_TABLE);
        ghcb_set_sw_exit_info_2(ghcb, 0);

        sev_es_wr_ghcb_msr(__pa(ghcb));
        VMGEXIT();

        if (ghcb_sw_exit_info_1_is_valid(ghcb) &&
            ghcb_sw_exit_info_2_is_valid(ghcb))
                ret = ghcb->save.sw_exit_info_2;

        __sev_put_ghcb(&state);

        local_irq_restore(flags);

        return ret;
}

int sev_es_setup_ap_jump_table(struct real_mode_header *rmh)
{
        u16 startup_cs, startup_ip;
        phys_addr_t jump_table_pa;
        u64 jump_table_addr;
        u16 __iomem *jump_table;

        jump_table_addr = get_jump_table_addr();

        /* On UP guests there is no jump table so this is not a failure */
        if (!jump_table_addr)
                return 0;

        /* Check if AP Jump Table is page-aligned */
        if (jump_table_addr & ~PAGE_MASK)
                return -EINVAL;

        jump_table_pa = jump_table_addr & PAGE_MASK;

        startup_cs = (u16)(rmh->trampoline_start >> 4);
        startup_ip = (u16)(rmh->sev_es_trampoline_start -
                           rmh->trampoline_start);

        jump_table = ioremap_encrypted(jump_table_pa, PAGE_SIZE);
        if (!jump_table)
                return -EIO;

        writew(startup_ip, &jump_table[0]);
        writew(startup_cs, &jump_table[1]);

        iounmap(jump_table);

        return 0;
}

/*
 * This is needed by the OVMF UEFI firmware which will use whatever it finds in
 * the GHCB MSR as its GHCB to talk to the hypervisor. So make sure the per-cpu
 * runtime GHCBs used by the kernel are also mapped in the EFI page-table.
 */
int __init sev_es_efi_map_ghcbs(pgd_t *pgd)
{
        struct sev_es_runtime_data *data;
        unsigned long address, pflags;
        int cpu;
        u64 pfn;

        if (!cc_platform_has(CC_ATTR_GUEST_STATE_ENCRYPT))
                return 0;

        pflags = _PAGE_NX | _PAGE_RW;

        for_each_possible_cpu(cpu) {
                data = per_cpu(runtime_data, cpu);

                address = __pa(&data->ghcb_page);
                pfn = address >> PAGE_SHIFT;

                if (kernel_map_pages_in_pgd(pgd, pfn, address, 1, pflags))
                        return 1;
        }

        return 0;
}

static enum es_result vc_handle_msr(struct ghcb *ghcb, struct es_em_ctxt *ctxt)
{
        struct pt_regs *regs = ctxt->regs;
        enum es_result ret;
        u64 exit_info_1;

        /* Is it a WRMSR? */
        exit_info_1 = (ctxt->insn.opcode.bytes[1] == 0x30) ? 1 : 0;

        ghcb_set_rcx(ghcb, regs->cx);
        if (exit_info_1) {
                ghcb_set_rax(ghcb, regs->ax);
                ghcb_set_rdx(ghcb, regs->dx);
        }

        ret = sev_es_ghcb_hv_call(ghcb, true, ctxt, SVM_EXIT_MSR,
                                  exit_info_1, 0);

        if ((ret == ES_OK) && (!exit_info_1)) {
                regs->ax = ghcb->save.rax;
                regs->dx = ghcb->save.rdx;
        }

        return ret;
}

/*
 * This function runs on the first #VC exception after the kernel
 * switched to virtual addresses.
 */
static bool __init sev_es_setup_ghcb(void)
{
        /* First make sure the hypervisor talks a supported protocol. */
        if (!sev_es_negotiate_protocol())
                return false;

        /*
         * Clear the boot_ghcb. The first exception comes in before the bss
         * section is cleared.
         */
        memset(&boot_ghcb_page, 0, PAGE_SIZE);

        /* Alright - Make the boot-ghcb public */
        boot_ghcb = &boot_ghcb_page;

        return true;
}

#ifdef CONFIG_HOTPLUG_CPU
static void sev_es_ap_hlt_loop(void)
{
        struct ghcb_state state;
        struct ghcb *ghcb;

        ghcb = __sev_get_ghcb(&state);

        while (true) {
                vc_ghcb_invalidate(ghcb);
                ghcb_set_sw_exit_code(ghcb, SVM_VMGEXIT_AP_HLT_LOOP);
                ghcb_set_sw_exit_info_1(ghcb, 0);
                ghcb_set_sw_exit_info_2(ghcb, 0);

                sev_es_wr_ghcb_msr(__pa(ghcb));
                VMGEXIT();

                /* Wakeup signal? */
                if (ghcb_sw_exit_info_2_is_valid(ghcb) &&
                    ghcb->save.sw_exit_info_2)
                        break;
        }

        __sev_put_ghcb(&state);
}

/*
 * Play_dead handler when running under SEV-ES. This is needed because
 * the hypervisor can't deliver an SIPI request to restart the AP.
 * Instead the kernel has to issue a VMGEXIT to halt the VCPU until the
 * hypervisor wakes it up again.
 */
static void sev_es_play_dead(void)
{
        play_dead_common();

        /* IRQs now disabled */

        sev_es_ap_hlt_loop();

        /*
         * If we get here, the VCPU was woken up again. Jump to CPU
         * startup code to get it back online.
         */
        start_cpu0();
}
#else  /* CONFIG_HOTPLUG_CPU */
#define sev_es_play_dead        native_play_dead
#endif /* CONFIG_HOTPLUG_CPU */

#ifdef CONFIG_SMP
static void __init sev_es_setup_play_dead(void)
{
        smp_ops.play_dead = sev_es_play_dead;
}
#else
static inline void sev_es_setup_play_dead(void) { }
#endif

static void __init alloc_runtime_data(int cpu)
{
        struct sev_es_runtime_data *data;

        data = memblock_alloc(sizeof(*data), PAGE_SIZE);
        if (!data)
                panic("Can't allocate SEV-ES runtime data");

        per_cpu(runtime_data, cpu) = data;
}

static void __init init_ghcb(int cpu)
{
        struct sev_es_runtime_data *data;
        int err;

        data = per_cpu(runtime_data, cpu);

        err = early_set_memory_decrypted((unsigned long)&data->ghcb_page,
                                         sizeof(data->ghcb_page));
        if (err)
                panic("Can't map GHCBs unencrypted");

        memset(&data->ghcb_page, 0, sizeof(data->ghcb_page));

        data->ghcb_active = false;
        data->backup_ghcb_active = false;
}

void __init sev_es_init_vc_handling(void)
{
        int cpu;

        BUILD_BUG_ON(offsetof(struct sev_es_runtime_data, ghcb_page) % PAGE_SIZE);

        if (!cc_platform_has(CC_ATTR_GUEST_STATE_ENCRYPT))
                return;

        if (!sev_es_check_cpu_features())
                panic("SEV-ES CPU Features missing");

        /* Enable SEV-ES special handling */
        static_branch_enable(&sev_es_enable_key);

        /* Initialize per-cpu GHCB pages */
        for_each_possible_cpu(cpu) {
                alloc_runtime_data(cpu);
                init_ghcb(cpu);
        }

        sev_es_setup_play_dead();

        /* Secondary CPUs use the runtime #VC handler */
        initial_vc_handler = (unsigned long)kernel_exc_vmm_communication;
}

static void __init vc_early_forward_exception(struct es_em_ctxt *ctxt)
{
        int trapnr = ctxt->fi.vector;

        if (trapnr == X86_TRAP_PF)
                native_write_cr2(ctxt->fi.cr2);

        ctxt->regs->orig_ax = ctxt->fi.error_code;
        do_early_exception(ctxt->regs, trapnr);
}

static long *vc_insn_get_rm(struct es_em_ctxt *ctxt)
{
        long *reg_array;
        int offset;

        reg_array = (long *)ctxt->regs;
        offset    = insn_get_modrm_rm_off(&ctxt->insn, ctxt->regs);

        if (offset < 0)
                return NULL;

        offset /= sizeof(long);

        return reg_array + offset;
}
static enum es_result vc_do_mmio(struct ghcb *ghcb, struct es_em_ctxt *ctxt,
                                 unsigned int bytes, bool read)
{
        u64 exit_code, exit_info_1, exit_info_2;
        unsigned long ghcb_pa = __pa(ghcb);
        enum es_result res;
        phys_addr_t paddr;
        void __user *ref;

        ref = insn_get_addr_ref(&ctxt->insn, ctxt->regs);
        if (ref == (void __user *)-1L)
                return ES_UNSUPPORTED;

        exit_code = read ? SVM_VMGEXIT_MMIO_READ : SVM_VMGEXIT_MMIO_WRITE;

        res = vc_slow_virt_to_phys(ghcb, ctxt, (unsigned long)ref, &paddr);
        if (res != ES_OK) {
                if (res == ES_EXCEPTION && !read)
                        ctxt->fi.error_code |= X86_PF_WRITE;

                return res;
        }

        exit_info_1 = paddr;
        /* Can never be greater than 8 */
        exit_info_2 = bytes;

        ghcb_set_sw_scratch(ghcb, ghcb_pa + offsetof(struct ghcb, shared_buffer));

        return sev_es_ghcb_hv_call(ghcb, true, ctxt, exit_code, exit_info_1, exit_info_2);
}

/*
 * The MOVS instruction has two memory operands, which raises the
 * problem that it is not known whether the access to the source or the
 * destination caused the #VC exception (and hence whether an MMIO read
 * or write operation needs to be emulated).
 *
 * Instead of playing games with walking page-tables and trying to guess
 * whether the source or destination is an MMIO range, split the move
 * into two operations, a read and a write with only one memory operand.
 * This will cause a nested #VC exception on the MMIO address which can
 * then be handled.
 *
 * This implementation has the benefit that it also supports MOVS where
 * source _and_ destination are MMIO regions.
 *
 * It will slow MOVS on MMIO down a lot, but in SEV-ES guests it is a
 * rare operation. If it turns out to be a performance problem the split
 * operations can be moved to memcpy_fromio() and memcpy_toio().
 */
static enum es_result vc_handle_mmio_movs(struct es_em_ctxt *ctxt,
                                          unsigned int bytes)
{
        unsigned long ds_base, es_base;
        unsigned char *src, *dst;
        unsigned char buffer[8];
        enum es_result ret;
        bool rep;
        int off;

        ds_base = insn_get_seg_base(ctxt->regs, INAT_SEG_REG_DS);
        es_base = insn_get_seg_base(ctxt->regs, INAT_SEG_REG_ES);

        if (ds_base == -1L || es_base == -1L) {
                ctxt->fi.vector = X86_TRAP_GP;
                ctxt->fi.error_code = 0;
                return ES_EXCEPTION;
        }

        src = ds_base + (unsigned char *)ctxt->regs->si;
        dst = es_base + (unsigned char *)ctxt->regs->di;

        ret = vc_read_mem(ctxt, src, buffer, bytes);
        if (ret != ES_OK)
                return ret;

        ret = vc_write_mem(ctxt, dst, buffer, bytes);
        if (ret != ES_OK)
                return ret;

        if (ctxt->regs->flags & X86_EFLAGS_DF)
                off = -bytes;
        else
                off =  bytes;

        ctxt->regs->si += off;
        ctxt->regs->di += off;

        rep = insn_has_rep_prefix(&ctxt->insn);
        if (rep)
                ctxt->regs->cx -= 1;

        if (!rep || ctxt->regs->cx == 0)
                return ES_OK;
        else
                return ES_RETRY;
}

static enum es_result vc_handle_mmio(struct ghcb *ghcb, struct es_em_ctxt *ctxt)
{
        struct insn *insn = &ctxt->insn;
        unsigned int bytes = 0;
        enum mmio_type mmio;
        enum es_result ret;
        u8 sign_byte;
        long *reg_data;

        mmio = insn_decode_mmio(insn, &bytes);
        if (mmio == MMIO_DECODE_FAILED)
                return ES_DECODE_FAILED;

        if (mmio != MMIO_WRITE_IMM && mmio != MMIO_MOVS) {
                reg_data = insn_get_modrm_reg_ptr(insn, ctxt->regs);
                if (!reg_data)
                        return ES_DECODE_FAILED;
        }

        switch (mmio) {
        case MMIO_WRITE:
                memcpy(ghcb->shared_buffer, reg_data, bytes);
                ret = vc_do_mmio(ghcb, ctxt, bytes, false);
                break;
        case MMIO_WRITE_IMM:
                memcpy(ghcb->shared_buffer, insn->immediate1.bytes, bytes);
                ret = vc_do_mmio(ghcb, ctxt, bytes, false);
                break;
        case MMIO_READ:
                ret = vc_do_mmio(ghcb, ctxt, bytes, true);
                if (ret)
                        break;

                /* Zero-extend for 32-bit operation */
                if (bytes == 4)
                        *reg_data = 0;

                memcpy(reg_data, ghcb->shared_buffer, bytes);
                break;
        case MMIO_READ_ZERO_EXTEND:
                ret = vc_do_mmio(ghcb, ctxt, bytes, true);
                if (ret)
                        break;

                /* Zero extend based on operand size */
                memset(reg_data, 0, insn->opnd_bytes);
                memcpy(reg_data, ghcb->shared_buffer, bytes);
                break;
        case MMIO_READ_SIGN_EXTEND:
                ret = vc_do_mmio(ghcb, ctxt, bytes, true);
                if (ret)
                        break;

                if (bytes == 1) {
                        u8 *val = (u8 *)ghcb->shared_buffer;

                        sign_byte = (*val & 0x80) ? 0xff : 0x00;
                } else {
                        u16 *val = (u16 *)ghcb->shared_buffer;

                        sign_byte = (*val & 0x8000) ? 0xff : 0x00;
                }

                /* Sign extend based on operand size */
                memset(reg_data, sign_byte, insn->opnd_bytes);
                memcpy(reg_data, ghcb->shared_buffer, bytes);
                break;
        case MMIO_MOVS:
                ret = vc_handle_mmio_movs(ctxt, bytes);
                break;
        default:
                ret = ES_UNSUPPORTED;
                break;
        }

        return ret;
}

static enum es_result vc_handle_dr7_write(struct ghcb *ghcb,
                                          struct es_em_ctxt *ctxt)
{
        struct sev_es_runtime_data *data = this_cpu_read(runtime_data);
        long val, *reg = vc_insn_get_rm(ctxt);
        enum es_result ret;

        if (!reg)
                return ES_DECODE_FAILED;

        val = *reg;

        /* Upper 32 bits must be written as zeroes */
        if (val >> 32) {
                ctxt->fi.vector = X86_TRAP_GP;
                ctxt->fi.error_code = 0;
                return ES_EXCEPTION;
        }

        /* Clear out other reserved bits and set bit 10 */
        val = (val & 0xffff23ffL) | BIT(10);

        /* Early non-zero writes to DR7 are not supported */
        if (!data && (val & ~DR7_RESET_VALUE))
                return ES_UNSUPPORTED;

        /* Using a value of 0 for ExitInfo1 means RAX holds the value */
        ghcb_set_rax(ghcb, val);
        ret = sev_es_ghcb_hv_call(ghcb, true, ctxt, SVM_EXIT_WRITE_DR7, 0, 0);
        if (ret != ES_OK)
                return ret;

        if (data)
                data->dr7 = val;

        return ES_OK;
}

static enum es_result vc_handle_dr7_read(struct ghcb *ghcb,
                                         struct es_em_ctxt *ctxt)
{
        struct sev_es_runtime_data *data = this_cpu_read(runtime_data);
        long *reg = vc_insn_get_rm(ctxt);

        if (!reg)
                return ES_DECODE_FAILED;

        if (data)
                *reg = data->dr7;
        else
                *reg = DR7_RESET_VALUE;

        return ES_OK;
}

static enum es_result vc_handle_wbinvd(struct ghcb *ghcb,
                                       struct es_em_ctxt *ctxt)
{
        return sev_es_ghcb_hv_call(ghcb, true, ctxt, SVM_EXIT_WBINVD, 0, 0);
}

static enum es_result vc_handle_rdpmc(struct ghcb *ghcb, struct es_em_ctxt *ctxt)
{
        enum es_result ret;

        ghcb_set_rcx(ghcb, ctxt->regs->cx);

        ret = sev_es_ghcb_hv_call(ghcb, true, ctxt, SVM_EXIT_RDPMC, 0, 0);
        if (ret != ES_OK)
                return ret;

        if (!(ghcb_rax_is_valid(ghcb) && ghcb_rdx_is_valid(ghcb)))
                return ES_VMM_ERROR;

        ctxt->regs->ax = ghcb->save.rax;
        ctxt->regs->dx = ghcb->save.rdx;

        return ES_OK;
}

static enum es_result vc_handle_monitor(struct ghcb *ghcb,
                                        struct es_em_ctxt *ctxt)
{
        /*
         * Treat it as a NOP and do not leak a physical address to the
         * hypervisor.
         */
        return ES_OK;
}

static enum es_result vc_handle_mwait(struct ghcb *ghcb,
                                      struct es_em_ctxt *ctxt)
{
        /* Treat the same as MONITOR/MONITORX */
        return ES_OK;
}

static enum es_result vc_handle_vmmcall(struct ghcb *ghcb,
                                        struct es_em_ctxt *ctxt)
{
        enum es_result ret;

        ghcb_set_rax(ghcb, ctxt->regs->ax);
        ghcb_set_cpl(ghcb, user_mode(ctxt->regs) ? 3 : 0);

        if (x86_platform.hyper.sev_es_hcall_prepare)
                x86_platform.hyper.sev_es_hcall_prepare(ghcb, ctxt->regs);

        ret = sev_es_ghcb_hv_call(ghcb, true, ctxt, SVM_EXIT_VMMCALL, 0, 0);
        if (ret != ES_OK)
                return ret;

        if (!ghcb_rax_is_valid(ghcb))
                return ES_VMM_ERROR;

        ctxt->regs->ax = ghcb->save.rax;

        /*
         * Call sev_es_hcall_finish() after regs->ax is already set.
         * This allows the hypervisor handler to overwrite it again if
         * necessary.
         */
        if (x86_platform.hyper.sev_es_hcall_finish &&
            !x86_platform.hyper.sev_es_hcall_finish(ghcb, ctxt->regs))
                return ES_VMM_ERROR;

        return ES_OK;
}

static enum es_result vc_handle_trap_ac(struct ghcb *ghcb,
                                        struct es_em_ctxt *ctxt)
{
        /*
         * Calling ecx_alignment_check() directly does not work, because it
         * enables IRQs and the GHCB is active. Forward the exception and call
         * it later from vc_forward_exception().
         */
        ctxt->fi.vector = X86_TRAP_AC;
        ctxt->fi.error_code = 0;
        return ES_EXCEPTION;
}

static enum es_result vc_handle_exitcode(struct es_em_ctxt *ctxt,
                                         struct ghcb *ghcb,
                                         unsigned long exit_code)
{
        enum es_result result;

        switch (exit_code) {
        case SVM_EXIT_READ_DR7:
                result = vc_handle_dr7_read(ghcb, ctxt);
                break;
        case SVM_EXIT_WRITE_DR7:
                result = vc_handle_dr7_write(ghcb, ctxt);
                break;
        case SVM_EXIT_EXCP_BASE + X86_TRAP_AC:
                result = vc_handle_trap_ac(ghcb, ctxt);
                break;
        case SVM_EXIT_RDTSC:
        case SVM_EXIT_RDTSCP:
                result = vc_handle_rdtsc(ghcb, ctxt, exit_code);
                break;
        case SVM_EXIT_RDPMC:
                result = vc_handle_rdpmc(ghcb, ctxt);
                break;
        case SVM_EXIT_INVD:
                pr_err_ratelimited("#VC exception for INVD??? Seriously???\n");
                result = ES_UNSUPPORTED;
                break;
        case SVM_EXIT_CPUID:
                result = vc_handle_cpuid(ghcb, ctxt);
                break;
        case SVM_EXIT_IOIO:
                result = vc_handle_ioio(ghcb, ctxt);
                break;
        case SVM_EXIT_MSR:
                result = vc_handle_msr(ghcb, ctxt);
                break;
        case SVM_EXIT_VMMCALL:
                result = vc_handle_vmmcall(ghcb, ctxt);
                break;
        case SVM_EXIT_WBINVD:
                result = vc_handle_wbinvd(ghcb, ctxt);
                break;
        case SVM_EXIT_MONITOR:
                result = vc_handle_monitor(ghcb, ctxt);
                break;
        case SVM_EXIT_MWAIT:
                result = vc_handle_mwait(ghcb, ctxt);
                break;
        case SVM_EXIT_NPF:
                result = vc_handle_mmio(ghcb, ctxt);
                break;
        default:
                /*
                 * Unexpected #VC exception
                 */
                result = ES_UNSUPPORTED;
        }

        return result;
}

static __always_inline void vc_forward_exception(struct es_em_ctxt *ctxt)
{
        long error_code = ctxt->fi.error_code;
        int trapnr = ctxt->fi.vector;

        ctxt->regs->orig_ax = ctxt->fi.error_code;

        switch (trapnr) {
        case X86_TRAP_GP:
                exc_general_protection(ctxt->regs, error_code);
                break;
        case X86_TRAP_UD:
                exc_invalid_op(ctxt->regs);
                break;
        case X86_TRAP_PF:
                write_cr2(ctxt->fi.cr2);
                exc_page_fault(ctxt->regs, error_code);
                break;
        case X86_TRAP_AC:
                exc_alignment_check(ctxt->regs, error_code);
                break;
        default:
                pr_emerg("Unsupported exception in #VC instruction emulation - can't continue\n");
                BUG();
        }
}

static __always_inline bool is_vc2_stack(unsigned long sp)
{
        return (sp >= __this_cpu_ist_bottom_va(VC2) && sp < __this_cpu_ist_top_va(VC2));
}

static __always_inline bool vc_from_invalid_context(struct pt_regs *regs)
{
        unsigned long sp, prev_sp;

        sp      = (unsigned long)regs;
        prev_sp = regs->sp;

        /*
         * If the code was already executing on the VC2 stack when the #VC
         * happened, let it proceed to the normal handling routine. This way the
         * code executing on the VC2 stack can cause #VC exceptions to get handled.
         */
        return is_vc2_stack(sp) && !is_vc2_stack(prev_sp);
}

static bool vc_raw_handle_exception(struct pt_regs *regs, unsigned long error_code)
{
        struct ghcb_state state;
        struct es_em_ctxt ctxt;
        enum es_result result;
        struct ghcb *ghcb;
        bool ret = true;

        ghcb = __sev_get_ghcb(&state);

        vc_ghcb_invalidate(ghcb);
        result = vc_init_em_ctxt(&ctxt, regs, error_code);

        if (result == ES_OK)
                result = vc_handle_exitcode(&ctxt, ghcb, error_code);

        __sev_put_ghcb(&state);

        /* Done - now check the result */
        switch (result) {
        case ES_OK:
                vc_finish_insn(&ctxt);
                break;
        case ES_UNSUPPORTED:
                pr_err_ratelimited("Unsupported exit-code 0x%02lx in #VC exception (IP: 0x%lx)\n",
                                   error_code, regs->ip);
                ret = false;
                break;
        case ES_VMM_ERROR:
                pr_err_ratelimited("Failure in communication with VMM (exit-code 0x%02lx IP: 0x%lx)\n",
                                   error_code, regs->ip);
                ret = false;
                break;
        case ES_DECODE_FAILED:
                pr_err_ratelimited("Failed to decode instruction (exit-code 0x%02lx IP: 0x%lx)\n",
                                   error_code, regs->ip);
                ret = false;
                break;
        case ES_EXCEPTION:
                vc_forward_exception(&ctxt);
                break;
        case ES_RETRY:
                /* Nothing to do */
                break;
        default:
                pr_emerg("Unknown result in %s():%d\n", __func__, result);
                /*
                 * Emulating the instruction which caused the #VC exception
                 * failed - can't continue so print debug information
                 */
                BUG();
        }

        return ret;
}

static __always_inline bool vc_is_db(unsigned long error_code)
{
        return error_code == SVM_EXIT_EXCP_BASE + X86_TRAP_DB;
}

/*
 * Runtime #VC exception handler when raised from kernel mode. Runs in NMI mode
 * and will panic when an error happens.
 */
DEFINE_IDTENTRY_VC_KERNEL(exc_vmm_communication)
{
        irqentry_state_t irq_state;

        /*
         * With the current implementation it is always possible to switch to a
         * safe stack because #VC exceptions only happen at known places, like
         * intercepted instructions or accesses to MMIO areas/IO ports. They can
         * also happen with code instrumentation when the hypervisor intercepts
         * #DB, but the critical paths are forbidden to be instrumented, so #DB
         * exceptions currently also only happen in safe places.
         *
         * But keep this here in case the noinstr annotations are violated due
         * to bug elsewhere.
         */
        if (unlikely(vc_from_invalid_context(regs))) {
                instrumentation_begin();
                panic("Can't handle #VC exception from unsupported context\n");
                instrumentation_end();
        }

        /*
         * Handle #DB before calling into !noinstr code to avoid recursive #DB.
         */
        if (vc_is_db(error_code)) {
                exc_debug(regs);
                return;
        }

        irq_state = irqentry_nmi_enter(regs);

        instrumentation_begin();

        if (!vc_raw_handle_exception(regs, error_code)) {
                /* Show some debug info */
                show_regs(regs);

                /* Ask hypervisor to sev_es_terminate */
                sev_es_terminate(GHCB_SEV_ES_GEN_REQ);

                /* If that fails and we get here - just panic */
                panic("Returned from Terminate-Request to Hypervisor\n");
        }

        instrumentation_end();
        irqentry_nmi_exit(regs, irq_state);
}

/*
 * Runtime #VC exception handler when raised from user mode. Runs in IRQ mode
 * and will kill the current task with SIGBUS when an error happens.
 */
DEFINE_IDTENTRY_VC_USER(exc_vmm_communication)
{
        /*
         * Handle #DB before calling into !noinstr code to avoid recursive #DB.
         */
        if (vc_is_db(error_code)) {
                noist_exc_debug(regs);
                return;
        }

        irqentry_enter_from_user_mode(regs);
        instrumentation_begin();

        if (!vc_raw_handle_exception(regs, error_code)) {
                /*
                 * Do not kill the machine if user-space triggered the
                 * exception. Send SIGBUS instead and let user-space deal with
                 * it.
                 */
                force_sig_fault(SIGBUS, BUS_OBJERR, (void __user *)0);
        }

        instrumentation_end();
        irqentry_exit_to_user_mode(regs);
}

bool __init handle_vc_boot_ghcb(struct pt_regs *regs)
{
        unsigned long exit_code = regs->orig_ax;
        struct es_em_ctxt ctxt;
        enum es_result result;

        /* Do initial setup or terminate the guest */
        if (unlikely(boot_ghcb == NULL && !sev_es_setup_ghcb()))
                sev_es_terminate(GHCB_SEV_ES_GEN_REQ);

        vc_ghcb_invalidate(boot_ghcb);

        result = vc_init_em_ctxt(&ctxt, regs, exit_code);
        if (result == ES_OK)
                result = vc_handle_exitcode(&ctxt, boot_ghcb, exit_code);

        /* Done - now check the result */
        switch (result) {
        case ES_OK:
                vc_finish_insn(&ctxt);
                break;
        case ES_UNSUPPORTED:
                early_printk("PANIC: Unsupported exit-code 0x%02lx in early #VC exception (IP: 0x%lx)\n",
                                exit_code, regs->ip);
                goto fail;
        case ES_VMM_ERROR:
                early_printk("PANIC: Failure in communication with VMM (exit-code 0x%02lx IP: 0x%lx)\n",
                                exit_code, regs->ip);
                goto fail;
        case ES_DECODE_FAILED:
                early_printk("PANIC: Failed to decode instruction (exit-code 0x%02lx IP: 0x%lx)\n",
                                exit_code, regs->ip);
                goto fail;
        case ES_EXCEPTION:
                vc_early_forward_exception(&ctxt);
                break;
        case ES_RETRY:
                /* Nothing to do */
                break;
        default:
                BUG();
        }

        return true;

fail:
        show_regs(regs);

        while (true)
                halt();
}