[linux.git] / arch / arm64 / kernel / fpsimd.c

/*
 * FP/SIMD context switching and fault handling
 *
 * Copyright (C) 2012 ARM Ltd.
 * Author: Catalin Marinas <[email protected]>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <linux/bottom_half.h>
#include <linux/cpu.h>
#include <linux/cpu_pm.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/percpu.h>
#include <linux/preempt.h>
#include <linux/sched/signal.h>
#include <linux/signal.h>

#include <asm/fpsimd.h>
#include <asm/cputype.h>
#include <asm/simd.h>

#define FPEXC_IOF	(1 << 0)
#define FPEXC_DZF	(1 << 1)
#define FPEXC_OFF	(1 << 2)
#define FPEXC_UFF	(1 << 3)
#define FPEXC_IXF	(1 << 4)
#define FPEXC_IDF	(1 << 7)

/*
 * In order to reduce the number of times the FPSIMD state is needlessly saved
 * and restored, we need to keep track of two things:
 * (a) for each task, we need to remember which CPU was the last one to have
 *     the task's FPSIMD state loaded into its FPSIMD registers;
 * (b) for each CPU, we need to remember which task's userland FPSIMD state has
 *     been loaded into its FPSIMD registers most recently, or whether it has
 *     been used to perform kernel mode NEON in the meantime.
 *
 * For (a), we add a 'cpu' field to struct fpsimd_state, which gets updated to
 * the id of the current CPU every time the state is loaded onto a CPU. For (b),
 * we add the per-cpu variable 'fpsimd_last_state' (below), which contains the
 * address of the userland FPSIMD state of the task that was loaded onto the CPU
 * the most recently, or NULL if kernel mode NEON has been performed after that.
 *
 * With this in place, we no longer have to restore the next FPSIMD state right
 * when switching between tasks. Instead, we can defer this check to userland
 * resume, at which time we verify whether the CPU's fpsimd_last_state and the
 * task's fpsimd_state.cpu are still mutually in sync. If this is the case, we
 * can omit the FPSIMD restore.
 *
 * As an optimization, we use the thread_info flag TIF_FOREIGN_FPSTATE to
 * indicate whether or not the userland FPSIMD state of the current task is
 * present in the registers. The flag is set unless the FPSIMD registers of this
 * CPU currently contain the most recent userland FPSIMD state of the current
 * task.
 *
 * In order to allow softirq handlers to use FPSIMD, kernel_neon_begin() may
 * save the task's FPSIMD context back to task_struct from softirq context.
 * To prevent this from racing with the manipulation of the task's FPSIMD state
 * from task context and thereby corrupting the state, it is necessary to
 * protect any manipulation of a task's fpsimd_state or TIF_FOREIGN_FPSTATE
 * flag with local_bh_disable() unless softirqs are already masked.
 *
 * For a certain task, the sequence may look something like this:
 * - the task gets scheduled in; if both the task's fpsimd_state.cpu field
 *   contains the id of the current CPU, and the CPU's fpsimd_last_state per-cpu
 *   variable points to the task's fpsimd_state, the TIF_FOREIGN_FPSTATE flag is
 *   cleared, otherwise it is set;
 *
 * - the task returns to userland; if TIF_FOREIGN_FPSTATE is set, the task's
 *   userland FPSIMD state is copied from memory to the registers, the task's
 *   fpsimd_state.cpu field is set to the id of the current CPU, the current
 *   CPU's fpsimd_last_state pointer is set to this task's fpsimd_state and the
 *   TIF_FOREIGN_FPSTATE flag is cleared;
 *
 * - the task executes an ordinary syscall; upon return to userland, the
 *   TIF_FOREIGN_FPSTATE flag will still be cleared, so no FPSIMD state is
 *   restored;
 *
 * - the task executes a syscall which executes some NEON instructions; this is
 *   preceded by a call to kernel_neon_begin(), which copies the task's FPSIMD
 *   register contents to memory, clears the fpsimd_last_state per-cpu variable
 *   and sets the TIF_FOREIGN_FPSTATE flag;
 *
 * - the task gets preempted after kernel_neon_end() is called; as we have not
 *   returned from the 2nd syscall yet, TIF_FOREIGN_FPSTATE is still set so
 *   whatever is in the FPSIMD registers is not saved to memory, but discarded.
 */
static DEFINE_PER_CPU(struct fpsimd_state *, fpsimd_last_state);

/*
 * Trapped FP/ASIMD access.
 */
void do_fpsimd_acc(unsigned int esr, struct pt_regs *regs)
{
	/* TODO: implement lazy context saving/restoring */
	WARN_ON(1);
}

/*
 * Raise a SIGFPE for the current process.
 */
void do_fpsimd_exc(unsigned int esr, struct pt_regs *regs)
{
	siginfo_t info;
	unsigned int si_code = 0;

	if (esr & FPEXC_IOF)
		si_code = FPE_FLTINV;
	else if (esr & FPEXC_DZF)
		si_code = FPE_FLTDIV;
	else if (esr & FPEXC_OFF)
		si_code = FPE_FLTOVF;
	else if (esr & FPEXC_UFF)
		si_code = FPE_FLTUND;
	else if (esr & FPEXC_IXF)
		si_code = FPE_FLTRES;

	memset(&info, 0, sizeof(info));
	info.si_signo = SIGFPE;
	info.si_code = si_code;
	info.si_addr = (void __user *)instruction_pointer(regs);

	send_sig_info(SIGFPE, &info, current);
}

void fpsimd_thread_switch(struct task_struct *next)
{
	if (!system_supports_fpsimd())
		return;
	/*
	 * Save the current FPSIMD state to memory, but only if whatever is in
	 * the registers is in fact the most recent userland FPSIMD state of
	 * 'current'.
	 */
	if (current->mm && !test_thread_flag(TIF_FOREIGN_FPSTATE))
		fpsimd_save_state(&current->thread.fpsimd_state);

	if (next->mm) {
		/*
		 * If we are switching to a task whose most recent userland
		 * FPSIMD state is already in the registers of *this* cpu,
		 * we can skip loading the state from memory. Otherwise, set
		 * the TIF_FOREIGN_FPSTATE flag so the state will be loaded
		 * upon the next return to userland.
		 */
		struct fpsimd_state *st = &next->thread.fpsimd_state;

		if (__this_cpu_read(fpsimd_last_state) == st
		    && st->cpu == smp_processor_id())
			clear_ti_thread_flag(task_thread_info(next),
					     TIF_FOREIGN_FPSTATE);
		else
			set_ti_thread_flag(task_thread_info(next),
					   TIF_FOREIGN_FPSTATE);
	}
}

void fpsimd_flush_thread(void)
{
	if (!system_supports_fpsimd())
		return;

	local_bh_disable();

	memset(&current->thread.fpsimd_state, 0, sizeof(struct fpsimd_state));
	fpsimd_flush_task_state(current);
	set_thread_flag(TIF_FOREIGN_FPSTATE);

	local_bh_enable();
}

/*
 * Save the userland FPSIMD state of 'current' to memory, but only if the state
 * currently held in the registers does in fact belong to 'current'
 */
void fpsimd_preserve_current_state(void)
{
	if (!system_supports_fpsimd())
		return;

	local_bh_disable();

	if (!test_thread_flag(TIF_FOREIGN_FPSTATE))
		fpsimd_save_state(&current->thread.fpsimd_state);

	local_bh_enable();
}

/*
 * Load the userland FPSIMD state of 'current' from memory, but only if the
 * FPSIMD state already held in the registers is /not/ the most recent FPSIMD
 * state of 'current'
 */
void fpsimd_restore_current_state(void)
{
	if (!system_supports_fpsimd())
		return;

	local_bh_disable();

	if (test_and_clear_thread_flag(TIF_FOREIGN_FPSTATE)) {
		struct fpsimd_state *st = &current->thread.fpsimd_state;

		fpsimd_load_state(st);
		__this_cpu_write(fpsimd_last_state, st);
		st->cpu = smp_processor_id();
	}

	local_bh_enable();
}

/*
 * Load an updated userland FPSIMD state for 'current' from memory and set the
 * flag that indicates that the FPSIMD register contents are the most recent
 * FPSIMD state of 'current'
 */
void fpsimd_update_current_state(struct fpsimd_state *state)
{
	if (!system_supports_fpsimd())
		return;

	local_bh_disable();

	fpsimd_load_state(state);
	if (test_and_clear_thread_flag(TIF_FOREIGN_FPSTATE)) {
		struct fpsimd_state *st = &current->thread.fpsimd_state;

		__this_cpu_write(fpsimd_last_state, st);
		st->cpu = smp_processor_id();
	}

	local_bh_enable();
}

/*
 * Invalidate live CPU copies of task t's FPSIMD state
 */
void fpsimd_flush_task_state(struct task_struct *t)
{
	t->thread.fpsimd_state.cpu = NR_CPUS;
}

#ifdef CONFIG_KERNEL_MODE_NEON

DEFINE_PER_CPU(bool, kernel_neon_busy);
EXPORT_PER_CPU_SYMBOL(kernel_neon_busy);

/*
 * Kernel-side NEON support functions
 */

/*
 * kernel_neon_begin(): obtain the CPU FPSIMD registers for use by the calling
 * context
 *
 * Must not be called unless may_use_simd() returns true.
 * Task context in the FPSIMD registers is saved back to memory as necessary.
 *
 * A matching call to kernel_neon_end() must be made before returning from the
 * calling context.
 *
 * The caller may freely use the FPSIMD registers until kernel_neon_end() is
 * called.
 */
void kernel_neon_begin(void)
{
	if (WARN_ON(!system_supports_fpsimd()))
		return;

	BUG_ON(!may_use_simd());

	local_bh_disable();

	__this_cpu_write(kernel_neon_busy, true);

	/* Save unsaved task fpsimd state, if any: */
	if (current->mm && !test_and_set_thread_flag(TIF_FOREIGN_FPSTATE))
		fpsimd_save_state(&current->thread.fpsimd_state);

	/* Invalidate any task state remaining in the fpsimd regs: */
	__this_cpu_write(fpsimd_last_state, NULL);

	preempt_disable();

	local_bh_enable();
}
EXPORT_SYMBOL(kernel_neon_begin);

/*
 * kernel_neon_end(): give the CPU FPSIMD registers back to the current task
 *
 * Must be called from a context in which kernel_neon_begin() was previously
 * called, with no call to kernel_neon_end() in the meantime.
 *
 * The caller must not use the FPSIMD registers after this function is called,
 * unless kernel_neon_begin() is called again in the meantime.
 */
void kernel_neon_end(void)
{
	bool busy;

	if (!system_supports_fpsimd())
		return;

	busy = __this_cpu_xchg(kernel_neon_busy, false);
	WARN_ON(!busy);	/* No matching kernel_neon_begin()? */

	preempt_enable();
}
EXPORT_SYMBOL(kernel_neon_end);

#ifdef CONFIG_EFI

static DEFINE_PER_CPU(struct fpsimd_state, efi_fpsimd_state);
static DEFINE_PER_CPU(bool, efi_fpsimd_state_used);

/*
 * EFI runtime services support functions
 *
 * The ABI for EFI runtime services allows EFI to use FPSIMD during the call.
 * This means that for EFI (and only for EFI), we have to assume that FPSIMD
 * is always used rather than being an optional accelerator.
 *
 * These functions provide the necessary support for ensuring FPSIMD
 * save/restore in the contexts from which EFI is used.
 *
 * Do not use them for any other purpose -- if tempted to do so, you are
 * either doing something wrong or you need to propose some refactoring.
 */

/*
 * __efi_fpsimd_begin(): prepare FPSIMD for making an EFI runtime services call
 */
void __efi_fpsimd_begin(void)
{
	if (!system_supports_fpsimd())
		return;

	WARN_ON(preemptible());

	if (may_use_simd())
		kernel_neon_begin();
	else {
		fpsimd_save_state(this_cpu_ptr(&efi_fpsimd_state));
		__this_cpu_write(efi_fpsimd_state_used, true);
	}
}

/*
 * __efi_fpsimd_end(): clean up FPSIMD after an EFI runtime services call
 */
void __efi_fpsimd_end(void)
{
	if (!system_supports_fpsimd())
		return;

	if (__this_cpu_xchg(efi_fpsimd_state_used, false))
		fpsimd_load_state(this_cpu_ptr(&efi_fpsimd_state));
	else
		kernel_neon_end();
}

#endif /* CONFIG_EFI */

#endif /* CONFIG_KERNEL_MODE_NEON */

#ifdef CONFIG_CPU_PM
static int fpsimd_cpu_pm_notifier(struct notifier_block *self,
				  unsigned long cmd, void *v)
{
	switch (cmd) {
	case CPU_PM_ENTER:
		if (current->mm && !test_thread_flag(TIF_FOREIGN_FPSTATE))
			fpsimd_save_state(&current->thread.fpsimd_state);
		this_cpu_write(fpsimd_last_state, NULL);
		break;
	case CPU_PM_EXIT:
		if (current->mm)
			set_thread_flag(TIF_FOREIGN_FPSTATE);
		break;
	case CPU_PM_ENTER_FAILED:
	default:
		return NOTIFY_DONE;
	}
	return NOTIFY_OK;
}

static struct notifier_block fpsimd_cpu_pm_notifier_block = {
	.notifier_call = fpsimd_cpu_pm_notifier,
};

static void __init fpsimd_pm_init(void)
{
	cpu_pm_register_notifier(&fpsimd_cpu_pm_notifier_block);
}

#else
static inline void fpsimd_pm_init(void) { }
#endif /* CONFIG_CPU_PM */

#ifdef CONFIG_HOTPLUG_CPU
static int fpsimd_cpu_dead(unsigned int cpu)
{
	per_cpu(fpsimd_last_state, cpu) = NULL;
	return 0;
}

static inline void fpsimd_hotplug_init(void)
{
	cpuhp_setup_state_nocalls(CPUHP_ARM64_FPSIMD_DEAD, "arm64/fpsimd:dead",
				  NULL, fpsimd_cpu_dead);
}

#else
static inline void fpsimd_hotplug_init(void) { }
#endif

/*
 * FP/SIMD support code initialisation.
 */
static int __init fpsimd_init(void)
{
	if (elf_hwcap & HWCAP_FP) {
		fpsimd_pm_init();
		fpsimd_hotplug_init();
	} else {
		pr_notice("Floating-point is not implemented\n");
	}

	if (!(elf_hwcap & HWCAP_ASIMD))
		pr_notice("Advanced SIMD is not implemented\n");

	return 0;
}
core_initcall(fpsimd_init);
Commit	Line	Data
53631b54 CM	1	/*
	2	* FP/SIMD context switching and fault handling
	3	*
	4	* Copyright (C) 2012 ARM Ltd.
	5	* Author: Catalin Marinas <[email protected]>
	6	*
	7	* This program is free software; you can redistribute it and/or modify
	8	* it under the terms of the GNU General Public License version 2 as
	9	* published by the Free Software Foundation.
	10	*
	11	* This program is distributed in the hope that it will be useful,
	12	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	13	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	14	* GNU General Public License for more details.
	15	*
	16	* You should have received a copy of the GNU General Public License
	17	* along with this program. If not, see <http://www.gnu.org/licenses/>.
	18	*/
	19
cb84d11e	20	#include <linux/bottom_half.h>
32365e64	21	#include <linux/cpu.h>
fb1ab1ab	22	#include <linux/cpu_pm.h>
53631b54 CM	23	#include <linux/kernel.h>
53631b54 CM	24	#include <linux/init.h>
cb84d11e	25	#include <linux/percpu.h>
4328825d	26	#include <linux/preempt.h>
3f07c014	27	#include <linux/sched/signal.h>
53631b54 CM	28	#include <linux/signal.h>
	29
	30	#include <asm/fpsimd.h>
	31	#include <asm/cputype.h>
4328825d	32	#include <asm/simd.h>
53631b54 CM	33
	34	#define FPEXC_IOF (1 << 0)
	35	#define FPEXC_DZF (1 << 1)
	36	#define FPEXC_OFF (1 << 2)
	37	#define FPEXC_UFF (1 << 3)
	38	#define FPEXC_IXF (1 << 4)
	39	#define FPEXC_IDF (1 << 7)
	40
005f78cd AB	41	/*
	42	* In order to reduce the number of times the FPSIMD state is needlessly saved
	43	* and restored, we need to keep track of two things:
	44	* (a) for each task, we need to remember which CPU was the last one to have
	45	* the task's FPSIMD state loaded into its FPSIMD registers;
	46	* (b) for each CPU, we need to remember which task's userland FPSIMD state has
	47	* been loaded into its FPSIMD registers most recently, or whether it has
	48	* been used to perform kernel mode NEON in the meantime.
	49	*
	50	* For (a), we add a 'cpu' field to struct fpsimd_state, which gets updated to
ef769e32	51	* the id of the current CPU every time the state is loaded onto a CPU. For (b),
005f78cd AB	52	* we add the per-cpu variable 'fpsimd_last_state' (below), which contains the
	53	* address of the userland FPSIMD state of the task that was loaded onto the CPU
	54	* the most recently, or NULL if kernel mode NEON has been performed after that.
	55	*
	56	* With this in place, we no longer have to restore the next FPSIMD state right
	57	* when switching between tasks. Instead, we can defer this check to userland
	58	* resume, at which time we verify whether the CPU's fpsimd_last_state and the
	59	* task's fpsimd_state.cpu are still mutually in sync. If this is the case, we
	60	* can omit the FPSIMD restore.
	61	*
	62	* As an optimization, we use the thread_info flag TIF_FOREIGN_FPSTATE to
	63	* indicate whether or not the userland FPSIMD state of the current task is
	64	* present in the registers. The flag is set unless the FPSIMD registers of this
	65	* CPU currently contain the most recent userland FPSIMD state of the current
	66	* task.
	67	*
cb84d11e DM	68	* In order to allow softirq handlers to use FPSIMD, kernel_neon_begin() may
	69	* save the task's FPSIMD context back to task_struct from softirq context.
	70	* To prevent this from racing with the manipulation of the task's FPSIMD state
	71	* from task context and thereby corrupting the state, it is necessary to
	72	* protect any manipulation of a task's fpsimd_state or TIF_FOREIGN_FPSTATE
	73	* flag with local_bh_disable() unless softirqs are already masked.
	74	*
005f78cd AB	75	* For a certain task, the sequence may look something like this:
	76	* - the task gets scheduled in; if both the task's fpsimd_state.cpu field
	77	* contains the id of the current CPU, and the CPU's fpsimd_last_state per-cpu
	78	* variable points to the task's fpsimd_state, the TIF_FOREIGN_FPSTATE flag is
	79	* cleared, otherwise it is set;
	80	*
	81	* - the task returns to userland; if TIF_FOREIGN_FPSTATE is set, the task's
	82	* userland FPSIMD state is copied from memory to the registers, the task's
	83	* fpsimd_state.cpu field is set to the id of the current CPU, the current
	84	* CPU's fpsimd_last_state pointer is set to this task's fpsimd_state and the
	85	* TIF_FOREIGN_FPSTATE flag is cleared;
	86	*
	87	* - the task executes an ordinary syscall; upon return to userland, the
	88	* TIF_FOREIGN_FPSTATE flag will still be cleared, so no FPSIMD state is
	89	* restored;
	90	*
	91	* - the task executes a syscall which executes some NEON instructions; this is
	92	* preceded by a call to kernel_neon_begin(), which copies the task's FPSIMD
	93	* register contents to memory, clears the fpsimd_last_state per-cpu variable
	94	* and sets the TIF_FOREIGN_FPSTATE flag;
	95	*
	96	* - the task gets preempted after kernel_neon_end() is called; as we have not
	97	* returned from the 2nd syscall yet, TIF_FOREIGN_FPSTATE is still set so
	98	* whatever is in the FPSIMD registers is not saved to memory, but discarded.
	99	*/
	100	static DEFINE_PER_CPU(struct fpsimd_state *, fpsimd_last_state);
	101
53631b54 CM	102	/*
	103	* Trapped FP/ASIMD access.
	104	*/
	105	void do_fpsimd_acc(unsigned int esr, struct pt_regs *regs)
	106	{
	107	/* TODO: implement lazy context saving/restoring */
	108	WARN_ON(1);
	109	}
	110
	111	/*
	112	* Raise a SIGFPE for the current process.
	113	*/
	114	void do_fpsimd_exc(unsigned int esr, struct pt_regs *regs)
	115	{
	116	siginfo_t info;
	117	unsigned int si_code = 0;
	118
	119	if (esr & FPEXC_IOF)
	120	si_code = FPE_FLTINV;
	121	else if (esr & FPEXC_DZF)
	122	si_code = FPE_FLTDIV;
	123	else if (esr & FPEXC_OFF)
	124	si_code = FPE_FLTOVF;
	125	else if (esr & FPEXC_UFF)
	126	si_code = FPE_FLTUND;
	127	else if (esr & FPEXC_IXF)
	128	si_code = FPE_FLTRES;
	129
	130	memset(&info, 0, sizeof(info));
	131	info.si_signo = SIGFPE;
	132	info.si_code = si_code;
	133	info.si_addr = (void __user *)instruction_pointer(regs);
	134
	135	send_sig_info(SIGFPE, &info, current);
	136	}
	137
	138	void fpsimd_thread_switch(struct task_struct *next)
	139	{
82e0191a SP	140	if (!system_supports_fpsimd())
82e0191a SP	141	return;
005f78cd AB	142	/*
	143	* Save the current FPSIMD state to memory, but only if whatever is in
	144	* the registers is in fact the most recent userland FPSIMD state of
	145	* 'current'.
	146	*/
	147	if (current->mm && !test_thread_flag(TIF_FOREIGN_FPSTATE))
53631b54	148	fpsimd_save_state(&current->thread.fpsimd_state);
005f78cd AB	149
	150	if (next->mm) {
	151	/*
	152	* If we are switching to a task whose most recent userland
	153	* FPSIMD state is already in the registers of this cpu,
	154	* we can skip loading the state from memory. Otherwise, set
	155	* the TIF_FOREIGN_FPSTATE flag so the state will be loaded
	156	* upon the next return to userland.
	157	*/
	158	struct fpsimd_state *st = &next->thread.fpsimd_state;
	159
	160	if (__this_cpu_read(fpsimd_last_state) == st
	161	&& st->cpu == smp_processor_id())
	162	clear_ti_thread_flag(task_thread_info(next),
	163	TIF_FOREIGN_FPSTATE);
	164	else
	165	set_ti_thread_flag(task_thread_info(next),
	166	TIF_FOREIGN_FPSTATE);
	167	}
53631b54 CM	168	}
	169
	170	void fpsimd_flush_thread(void)
	171	{
82e0191a SP	172	if (!system_supports_fpsimd())
82e0191a SP	173	return;
cb84d11e DM	174
	175	local_bh_disable();
	176
53631b54	177	memset(&current->thread.fpsimd_state, 0, sizeof(struct fpsimd_state));
674c242c	178	fpsimd_flush_task_state(current);
005f78cd	179	set_thread_flag(TIF_FOREIGN_FPSTATE);
cb84d11e DM	180
cb84d11e DM	181	local_bh_enable();
53631b54 CM	182	}
53631b54 CM	183
c51f9269	184	/*
005f78cd AB	185	* Save the userland FPSIMD state of 'current' to memory, but only if the state
005f78cd AB	186	* currently held in the registers does in fact belong to 'current'
c51f9269 AB	187	*/
	188	void fpsimd_preserve_current_state(void)
	189	{
82e0191a SP	190	if (!system_supports_fpsimd())
82e0191a SP	191	return;
cb84d11e DM	192
	193	local_bh_disable();
	194
005f78cd AB	195	if (!test_thread_flag(TIF_FOREIGN_FPSTATE))
005f78cd AB	196	fpsimd_save_state(&current->thread.fpsimd_state);
cb84d11e DM	197
cb84d11e DM	198	local_bh_enable();
c51f9269 AB	199	}
	200
	201	/*
005f78cd AB	202	* Load the userland FPSIMD state of 'current' from memory, but only if the
	203	* FPSIMD state already held in the registers is /not/ the most recent FPSIMD
	204	* state of 'current'
	205	*/
	206	void fpsimd_restore_current_state(void)
	207	{
82e0191a SP	208	if (!system_supports_fpsimd())
82e0191a SP	209	return;
cb84d11e DM	210
	211	local_bh_disable();
	212
005f78cd AB	213	if (test_and_clear_thread_flag(TIF_FOREIGN_FPSTATE)) {
	214	struct fpsimd_state *st = &current->thread.fpsimd_state;
	215
	216	fpsimd_load_state(st);
50464185	217	__this_cpu_write(fpsimd_last_state, st);
005f78cd AB	218	st->cpu = smp_processor_id();
005f78cd AB	219	}
cb84d11e DM	220
cb84d11e DM	221	local_bh_enable();
005f78cd AB	222	}
	223
	224	/*
	225	* Load an updated userland FPSIMD state for 'current' from memory and set the
	226	* flag that indicates that the FPSIMD register contents are the most recent
	227	* FPSIMD state of 'current'
c51f9269 AB	228	*/
	229	void fpsimd_update_current_state(struct fpsimd_state *state)
	230	{
82e0191a SP	231	if (!system_supports_fpsimd())
82e0191a SP	232	return;
cb84d11e DM	233
	234	local_bh_disable();
	235
c51f9269	236	fpsimd_load_state(state);
005f78cd AB	237	if (test_and_clear_thread_flag(TIF_FOREIGN_FPSTATE)) {
	238	struct fpsimd_state *st = &current->thread.fpsimd_state;
	239
50464185	240	__this_cpu_write(fpsimd_last_state, st);
005f78cd AB	241	st->cpu = smp_processor_id();
005f78cd AB	242	}
cb84d11e DM	243
cb84d11e DM	244	local_bh_enable();
c51f9269 AB	245	}
c51f9269 AB	246
005f78cd AB	247	/*
	248	* Invalidate live CPU copies of task t's FPSIMD state
	249	*/
	250	void fpsimd_flush_task_state(struct task_struct *t)
	251	{
	252	t->thread.fpsimd_state.cpu = NR_CPUS;
	253	}
	254
4cfb3613 AB	255	#ifdef CONFIG_KERNEL_MODE_NEON
4cfb3613 AB	256
cb84d11e	257	DEFINE_PER_CPU(bool, kernel_neon_busy);
11cefd5a	258	EXPORT_PER_CPU_SYMBOL(kernel_neon_busy);
190f1ca8	259
4cfb3613 AB	260	/*
	261	* Kernel-side NEON support functions
	262	*/
cb84d11e DM	263
	264	/*
	265	* kernel_neon_begin(): obtain the CPU FPSIMD registers for use by the calling
	266	* context
	267	*
	268	* Must not be called unless may_use_simd() returns true.
	269	* Task context in the FPSIMD registers is saved back to memory as necessary.
	270	*
	271	* A matching call to kernel_neon_end() must be made before returning from the
	272	* calling context.
	273	*
	274	* The caller may freely use the FPSIMD registers until kernel_neon_end() is
	275	* called.
	276	*/
	277	void kernel_neon_begin(void)
4cfb3613	278	{
82e0191a SP	279	if (WARN_ON(!system_supports_fpsimd()))
82e0191a SP	280	return;
4cfb3613	281
cb84d11e DM	282	BUG_ON(!may_use_simd());
	283
	284	local_bh_disable();
	285
	286	__this_cpu_write(kernel_neon_busy, true);
	287
	288	/* Save unsaved task fpsimd state, if any: */
	289	if (current->mm && !test_and_set_thread_flag(TIF_FOREIGN_FPSTATE))
	290	fpsimd_save_state(&current->thread.fpsimd_state);
	291
	292	/* Invalidate any task state remaining in the fpsimd regs: */
	293	__this_cpu_write(fpsimd_last_state, NULL);
	294
	295	preempt_disable();
	296
	297	local_bh_enable();
4cfb3613	298	}
cb84d11e	299	EXPORT_SYMBOL(kernel_neon_begin);
4cfb3613	300
cb84d11e DM	301	/*
	302	* kernel_neon_end(): give the CPU FPSIMD registers back to the current task
	303	*
	304	* Must be called from a context in which kernel_neon_begin() was previously
	305	* called, with no call to kernel_neon_end() in the meantime.
	306	*
	307	* The caller must not use the FPSIMD registers after this function is called,
	308	* unless kernel_neon_begin() is called again in the meantime.
	309	*/
4cfb3613 AB	310	void kernel_neon_end(void)
4cfb3613 AB	311	{
cb84d11e DM	312	bool busy;
cb84d11e DM	313
82e0191a SP	314	if (!system_supports_fpsimd())
82e0191a SP	315	return;
cb84d11e DM	316
	317	busy = __this_cpu_xchg(kernel_neon_busy, false);
	318	WARN_ON(!busy); /* No matching kernel_neon_begin()? */
	319
	320	preempt_enable();
4cfb3613 AB	321	}
	322	EXPORT_SYMBOL(kernel_neon_end);
	323
e580b8bc DM	324	#ifdef CONFIG_EFI
e580b8bc DM	325
3b66023d DM	326	static DEFINE_PER_CPU(struct fpsimd_state, efi_fpsimd_state);
3b66023d DM	327	static DEFINE_PER_CPU(bool, efi_fpsimd_state_used);
4328825d DM	328
	329	/*
	330	* EFI runtime services support functions
	331	*
	332	* The ABI for EFI runtime services allows EFI to use FPSIMD during the call.
	333	* This means that for EFI (and only for EFI), we have to assume that FPSIMD
	334	* is always used rather than being an optional accelerator.
	335	*
	336	* These functions provide the necessary support for ensuring FPSIMD
	337	* save/restore in the contexts from which EFI is used.
	338	*
	339	* Do not use them for any other purpose -- if tempted to do so, you are
	340	* either doing something wrong or you need to propose some refactoring.
	341	*/
	342
	343	/*
	344	* __efi_fpsimd_begin(): prepare FPSIMD for making an EFI runtime services call
	345	*/
	346	void __efi_fpsimd_begin(void)
	347	{
	348	if (!system_supports_fpsimd())
	349	return;
	350
	351	WARN_ON(preemptible());
	352
	353	if (may_use_simd())
	354	kernel_neon_begin();
	355	else {
	356	fpsimd_save_state(this_cpu_ptr(&efi_fpsimd_state));
	357	__this_cpu_write(efi_fpsimd_state_used, true);
	358	}
	359	}
	360
	361	/*
	362	* __efi_fpsimd_end(): clean up FPSIMD after an EFI runtime services call
	363	*/
	364	void __efi_fpsimd_end(void)
	365	{
	366	if (!system_supports_fpsimd())
	367	return;
	368
	369	if (__this_cpu_xchg(efi_fpsimd_state_used, false))
	370	fpsimd_load_state(this_cpu_ptr(&efi_fpsimd_state));
	371	else
	372	kernel_neon_end();
	373	}
	374
e580b8bc DM	375	#endif /* CONFIG_EFI */
e580b8bc DM	376
4cfb3613 AB	377	#endif /* CONFIG_KERNEL_MODE_NEON */
4cfb3613 AB	378
fb1ab1ab LP	379	#ifdef CONFIG_CPU_PM
	380	static int fpsimd_cpu_pm_notifier(struct notifier_block *self,
	381	unsigned long cmd, void *v)
	382	{
	383	switch (cmd) {
	384	case CPU_PM_ENTER:
005f78cd	385	if (current->mm && !test_thread_flag(TIF_FOREIGN_FPSTATE))
fb1ab1ab	386	fpsimd_save_state(&current->thread.fpsimd_state);
7c68a9cc	387	this_cpu_write(fpsimd_last_state, NULL);
fb1ab1ab LP	388	break;
	389	case CPU_PM_EXIT:
	390	if (current->mm)
005f78cd	391	set_thread_flag(TIF_FOREIGN_FPSTATE);
fb1ab1ab LP	392	break;
	393	case CPU_PM_ENTER_FAILED:
	394	default:
	395	return NOTIFY_DONE;
	396	}
	397	return NOTIFY_OK;
	398	}
	399
	400	static struct notifier_block fpsimd_cpu_pm_notifier_block = {
	401	.notifier_call = fpsimd_cpu_pm_notifier,
	402	};
	403
a7c61a34	404	static void __init fpsimd_pm_init(void)
fb1ab1ab LP	405	{
	406	cpu_pm_register_notifier(&fpsimd_cpu_pm_notifier_block);
	407	}
	408
	409	#else
	410	static inline void fpsimd_pm_init(void) { }
	411	#endif /* CONFIG_CPU_PM */
	412
32365e64	413	#ifdef CONFIG_HOTPLUG_CPU
c23a7266	414	static int fpsimd_cpu_dead(unsigned int cpu)
32365e64	415	{
c23a7266 SAS	416	per_cpu(fpsimd_last_state, cpu) = NULL;
c23a7266 SAS	417	return 0;
32365e64 JL	418	}
32365e64 JL	419
32365e64 JL	420	static inline void fpsimd_hotplug_init(void)
32365e64 JL	421	{
c23a7266 SAS	422	cpuhp_setup_state_nocalls(CPUHP_ARM64_FPSIMD_DEAD, "arm64/fpsimd:dead",
c23a7266 SAS	423	NULL, fpsimd_cpu_dead);
32365e64 JL	424	}
	425
	426	#else
	427	static inline void fpsimd_hotplug_init(void) { }
	428	#endif
	429
53631b54 CM	430	/*
	431	* FP/SIMD support code initialisation.
	432	*/
	433	static int __init fpsimd_init(void)
	434	{
fe80f9f2 SP	435	if (elf_hwcap & HWCAP_FP) {
	436	fpsimd_pm_init();
	437	fpsimd_hotplug_init();
	438	} else {
53631b54	439	pr_notice("Floating-point is not implemented\n");
53631b54	440	}
53631b54	441
fe80f9f2	442	if (!(elf_hwcap & HWCAP_ASIMD))
53631b54	443	pr_notice("Advanced SIMD is not implemented\n");
fb1ab1ab	444
53631b54 CM	445	return 0;
53631b54 CM	446	}
ae2e972d	447	core_initcall(fpsimd_init);