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Commit 421ec901 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge branch 'x86-fpu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 

Pull x86 fpu changes from Ingo Molnar:
 "Various x86 FPU handling cleanups, refactorings and fixes (Borislav
  Petkov, Oleg Nesterov, Rik van Riel)"

* 'x86-fpu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (21 commits)
  x86/fpu: Kill eager_fpu_init_bp()
  x86/fpu: Don't allocate fpu->state for swapper/0
  x86/fpu: Rename drop_init_fpu() to fpu_reset_state()
  x86/fpu: Fold __drop_fpu() into its sole user
  x86/fpu: Don't abuse drop_init_fpu() in flush_thread()
  x86/fpu: Use restore_init_xstate() instead of math_state_restore() on kthread exec
  x86/fpu: Introduce restore_init_xstate()
  x86/fpu: Document user_fpu_begin()
  x86/fpu: Factor out memset(xstate, 0) in fpu_finit() paths
  x86/fpu: Change xstateregs_get()/set() to use ->xsave.i387 rather than ->fxsave
  x86/fpu: Don't abuse FPU in kernel threads if use_eager_fpu()
  x86/fpu: Always allow FPU in interrupt if use_eager_fpu()
  x86/fpu: __kernel_fpu_begin() should clear fpu_owner_task even if use_eager_fpu()
  x86/fpu: Also check fpu_lazy_restore() when use_eager_fpu()
  x86/fpu: Use task_disable_lazy_fpu_restore() helper
  x86/fpu: Use an explicit if/else in switch_fpu_prepare()
  x86/fpu: Introduce task_disable_lazy_fpu_restore() helper
  x86/fpu: Move lazy restore functions up a few lines
  x86/fpu: Change math_error() to use unlazy_fpu(), kill (now) unused save_init_fpu()
  x86/fpu: Don't do __thread_fpu_end() if use_eager_fpu()
  ...
parents 64f004a2 7fc253e2

arch/x86/include/asm/fpu-internal.h

+66 −64
Original line number Diff line number Diff line
@@ -67,6 +67,34 @@ extern void finit_soft_fpu(struct i387_soft_struct *soft); 
static inline void finit_soft_fpu(struct i387_soft_struct *soft) {}

#endif



/*

 * Must be run with preemption disabled: this clears the fpu_owner_task,

 * on this CPU.

 *

 * This will disable any lazy FPU state restore of the current FPU state,

 * but if the current thread owns the FPU, it will still be saved by.

 */

static inline void __cpu_disable_lazy_restore(unsigned int cpu)

{

	per_cpu(fpu_owner_task, cpu) = NULL;

}



/*

 * Used to indicate that the FPU state in memory is newer than the FPU

 * state in registers, and the FPU state should be reloaded next time the

 * task is run. Only safe on the current task, or non-running tasks.

 */

static inline void task_disable_lazy_fpu_restore(struct task_struct *tsk)

{

	tsk->thread.fpu.last_cpu = ~0;

}



static inline int fpu_lazy_restore(struct task_struct *new, unsigned int cpu)

{

	return new == this_cpu_read_stable(fpu_owner_task) &&

		cpu == new->thread.fpu.last_cpu;

}



static inline int is_ia32_compat_frame(void)

{

	return config_enabled(CONFIG_IA32_EMULATION) &&
@@ -107,7 +135,6 @@ static __always_inline __pure bool use_fxsr(void) 


static inline void fx_finit(struct i387_fxsave_struct *fx)

{

	memset(fx, 0, xstate_size);

	fx->cwd = 0x37f;

	fx->mxcsr = MXCSR_DEFAULT;

}
@@ -351,8 +378,14 @@ static inline void __thread_fpu_begin(struct task_struct *tsk) 
	__thread_set_has_fpu(tsk);

}



static inline void __drop_fpu(struct task_struct *tsk)

static inline void drop_fpu(struct task_struct *tsk)

{

	/*

	 * Forget coprocessor state..

	 */

	preempt_disable();

	tsk->thread.fpu_counter = 0;



	if (__thread_has_fpu(tsk)) {

		/* Ignore delayed exceptions from user space */

		asm volatile("1: fwait\n"
@@ -360,30 +393,29 @@ static inline void __drop_fpu(struct task_struct *tsk) 
			     _ASM_EXTABLE(1b, 2b));

		__thread_fpu_end(tsk);

	}

}



static inline void drop_fpu(struct task_struct *tsk)

{

	/*

	 * Forget coprocessor state..

	 */

	preempt_disable();

	tsk->thread.fpu_counter = 0;

	__drop_fpu(tsk);

	clear_stopped_child_used_math(tsk);

	preempt_enable();

}



static inline void drop_init_fpu(struct task_struct *tsk)

static inline void restore_init_xstate(void)

{

	if (!use_eager_fpu())

		drop_fpu(tsk);

	else {

	if (use_xsave())

		xrstor_state(init_xstate_buf, -1);

	else

		fxrstor_checking(&init_xstate_buf->i387);

}



/*

 * Reset the FPU state in the eager case and drop it in the lazy case (later use

 * will reinit it).

 */

static inline void fpu_reset_state(struct task_struct *tsk)

{

	if (!use_eager_fpu())

		drop_fpu(tsk);

	else

		restore_init_xstate();

}



/*
@@ -400,24 +432,6 @@ static inline void drop_init_fpu(struct task_struct *tsk) 
 */

typedef struct { int preload; } fpu_switch_t;



/*

 * Must be run with preemption disabled: this clears the fpu_owner_task,

 * on this CPU.

 *

 * This will disable any lazy FPU state restore of the current FPU state,

 * but if the current thread owns the FPU, it will still be saved by.

 */

static inline void __cpu_disable_lazy_restore(unsigned int cpu)

{

	per_cpu(fpu_owner_task, cpu) = NULL;

}



static inline int fpu_lazy_restore(struct task_struct *new, unsigned int cpu)

{

	return new == this_cpu_read_stable(fpu_owner_task) &&

		cpu == new->thread.fpu.last_cpu;

}



static inline fpu_switch_t switch_fpu_prepare(struct task_struct *old, struct task_struct *new, int cpu)

{

	fpu_switch_t fpu;
@@ -426,13 +440,17 @@ static inline fpu_switch_t switch_fpu_prepare(struct task_struct *old, struct ta 
	 * If the task has used the math, pre-load the FPU on xsave processors

	 * or if the past 5 consecutive context-switches used math.

	 */

	fpu.preload = tsk_used_math(new) && (use_eager_fpu() ||

					     new->thread.fpu_counter > 5);

	fpu.preload = tsk_used_math(new) &&

		      (use_eager_fpu() || new->thread.fpu_counter > 5);



	if (__thread_has_fpu(old)) {

		if (!__save_init_fpu(old))

			cpu = ~0;

			task_disable_lazy_fpu_restore(old);

		else

			old->thread.fpu.last_cpu = cpu;

		old->thread.fpu.has_fpu = 0;	/* But leave fpu_owner_task! */



		/* But leave fpu_owner_task! */

		old->thread.fpu.has_fpu = 0;



		/* Don't change CR0.TS if we just switch! */

		if (fpu.preload) {
@@ -443,10 +461,10 @@ static inline fpu_switch_t switch_fpu_prepare(struct task_struct *old, struct ta 
			stts();

	} else {

		old->thread.fpu_counter = 0;

		old->thread.fpu.last_cpu = ~0;

		task_disable_lazy_fpu_restore(old);

		if (fpu.preload) {

			new->thread.fpu_counter++;

			if (!use_eager_fpu() && fpu_lazy_restore(new, cpu))

			if (fpu_lazy_restore(new, cpu))

				fpu.preload = 0;

			else

				prefetch(new->thread.fpu.state);
@@ -466,7 +484,7 @@ static inline void switch_fpu_finish(struct task_struct *new, fpu_switch_t fpu) 
{

	if (fpu.preload) {

		if (unlikely(restore_fpu_checking(new)))

			drop_init_fpu(new);

			fpu_reset_state(new);

	}

}
@@ -495,10 +513,12 @@ static inline int restore_xstate_sig(void __user *buf, int ia32_frame) 
}



/*

 * Need to be preemption-safe.

 * Needs to be preemption-safe.

 *

 * NOTE! user_fpu_begin() must be used only immediately before restoring

 * it. This function does not do any save/restore on their own.

 * the save state. It does not do any saving/restoring on its own. In

 * lazy FPU mode, it is just an optimization to avoid a #NM exception,

 * the task can lose the FPU right after preempt_enable().

 */

static inline void user_fpu_begin(void)

{
@@ -519,24 +539,6 @@ static inline void __save_fpu(struct task_struct *tsk) 
		fpu_fxsave(&tsk->thread.fpu);

}



/*

 * These disable preemption on their own and are safe

 */

static inline void save_init_fpu(struct task_struct *tsk)

{

	WARN_ON_ONCE(!__thread_has_fpu(tsk));



	if (use_eager_fpu()) {

		__save_fpu(tsk);

		return;

	}



	preempt_disable();

	__save_init_fpu(tsk);

	__thread_fpu_end(tsk);

	preempt_enable();

}



/*

 * i387 state interaction

 */

arch/x86/kernel/i387.c

+26 −28
Original line number Diff line number Diff line
@@ -42,8 +42,8 @@ void kernel_fpu_enable(void) 
 * be set (so that the clts/stts pair does nothing that is

 * visible in the interrupted kernel thread).

 *

 * Except for the eagerfpu case when we return 1 unless we've already

 * been eager and saved the state in kernel_fpu_begin().

 * Except for the eagerfpu case when we return true; in the likely case

 * the thread has FPU but we are not going to set/clear TS.

 */

static inline bool interrupted_kernel_fpu_idle(void)

{
@@ -51,7 +51,7 @@ static inline bool interrupted_kernel_fpu_idle(void) 
		return false;



	if (use_eager_fpu())

		return __thread_has_fpu(current);

		return true;



	return !__thread_has_fpu(current) &&

		(read_cr0() & X86_CR0_TS);
@@ -94,8 +94,9 @@ void __kernel_fpu_begin(void) 


	if (__thread_has_fpu(me)) {

		__save_init_fpu(me);

	} else if (!use_eager_fpu()) {

	} else {

		this_cpu_write(fpu_owner_task, NULL);

		if (!use_eager_fpu())

			clts();

	}

}
@@ -107,7 +108,7 @@ void __kernel_fpu_end(void) 


	if (__thread_has_fpu(me)) {

		if (WARN_ON(restore_fpu_checking(me)))

			drop_init_fpu(me);

			fpu_reset_state(me);

	} else if (!use_eager_fpu()) {

		stts();

	}
@@ -120,10 +121,13 @@ void unlazy_fpu(struct task_struct *tsk) 
{

	preempt_disable();

	if (__thread_has_fpu(tsk)) {

		if (use_eager_fpu()) {

			__save_fpu(tsk);

		} else {

			__save_init_fpu(tsk);

			__thread_fpu_end(tsk);

	} else

		tsk->thread.fpu_counter = 0;

		}

	}

	preempt_enable();

}

EXPORT_SYMBOL(unlazy_fpu);
@@ -221,11 +225,12 @@ void fpu_finit(struct fpu *fpu) 
		return;

	}



	memset(fpu->state, 0, xstate_size);



	if (cpu_has_fxsr) {

		fx_finit(&fpu->state->fxsave);

	} else {

		struct i387_fsave_struct *fp = &fpu->state->fsave;

		memset(fp, 0, xstate_size);

		fp->cwd = 0xffff037fu;

		fp->swd = 0xffff0000u;

		fp->twd = 0xffffffffu;
@@ -247,7 +252,7 @@ int init_fpu(struct task_struct *tsk) 
	if (tsk_used_math(tsk)) {

		if (cpu_has_fpu && tsk == current)

			unlazy_fpu(tsk);

		tsk->thread.fpu.last_cpu = ~0;

		task_disable_lazy_fpu_restore(tsk);

		return 0;

	}
@@ -336,6 +341,7 @@ int xstateregs_get(struct task_struct *target, const struct user_regset *regset, 
		unsigned int pos, unsigned int count,

		void *kbuf, void __user *ubuf)

{

	struct xsave_struct *xsave = &target->thread.fpu.state->xsave;

	int ret;



	if (!cpu_has_xsave)
@@ -350,14 +356,12 @@ int xstateregs_get(struct task_struct *target, const struct user_regset *regset, 
	 * memory layout in the thread struct, so that we can copy the entire

	 * xstateregs to the user using one user_regset_copyout().

	 */

	memcpy(&target->thread.fpu.state->fxsave.sw_reserved,

	memcpy(&xsave->i387.sw_reserved,

		xstate_fx_sw_bytes, sizeof(xstate_fx_sw_bytes));



	/*

	 * Copy the xstate memory layout.

	 */

	ret = user_regset_copyout(&pos, &count, &kbuf, &ubuf,

				  &target->thread.fpu.state->xsave, 0, -1);

	ret = user_regset_copyout(&pos, &count, &kbuf, &ubuf, xsave, 0, -1);

	return ret;

}
@@ -365,8 +369,8 @@ int xstateregs_set(struct task_struct *target, const struct user_regset *regset, 
		  unsigned int pos, unsigned int count,

		  const void *kbuf, const void __user *ubuf)

{

	struct xsave_struct *xsave = &target->thread.fpu.state->xsave;

	int ret;

	struct xsave_hdr_struct *xsave_hdr;



	if (!cpu_has_xsave)

		return -ENODEV;
@@ -375,22 +379,16 @@ int xstateregs_set(struct task_struct *target, const struct user_regset *regset, 
	if (ret)

		return ret;



	ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf,

				 &target->thread.fpu.state->xsave, 0, -1);



	ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, xsave, 0, -1);

	/*

	 * mxcsr reserved bits must be masked to zero for security reasons.

	 */

	target->thread.fpu.state->fxsave.mxcsr &= mxcsr_feature_mask;



	xsave_hdr = &target->thread.fpu.state->xsave.xsave_hdr;



	xsave_hdr->xstate_bv &= pcntxt_mask;

	xsave->i387.mxcsr &= mxcsr_feature_mask;

	xsave->xsave_hdr.xstate_bv &= pcntxt_mask;

	/*

	 * These bits must be zero.

	 */

	memset(xsave_hdr->reserved, 0, 48);



	memset(&xsave->xsave_hdr.reserved, 0, 48);

	return ret;

}

arch/x86/kernel/process.c

+12 −7
Original line number Diff line number Diff line
@@ -89,8 +89,8 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src) 


	dst->thread.fpu_counter = 0;

	dst->thread.fpu.has_fpu = 0;

	dst->thread.fpu.last_cpu = ~0;

	dst->thread.fpu.state = NULL;

	task_disable_lazy_fpu_restore(dst);

	if (tsk_used_math(src)) {

		int err = fpu_alloc(&dst->thread.fpu);

		if (err)
@@ -151,13 +151,18 @@ void flush_thread(void) 


	flush_ptrace_hw_breakpoint(tsk);

	memset(tsk->thread.tls_array, 0, sizeof(tsk->thread.tls_array));

	drop_init_fpu(tsk);

	/*

	 * Free the FPU state for non xsave platforms. They get reallocated

	 * lazily at the first use.

	 */

	if (!use_eager_fpu())



	if (!use_eager_fpu()) {

		/* FPU state will be reallocated lazily at the first use. */

		drop_fpu(tsk);

		free_thread_xstate(tsk);

	} else if (!used_math()) {

		/* kthread execs. TODO: cleanup this horror. */

		if (WARN_ON(init_fpu(tsk)))

			force_sig(SIGKILL, tsk);

		user_fpu_begin();

		restore_init_xstate();

	}

}



static void hard_disable_TSC(void)

arch/x86/kernel/signal.c

+1 −1
Original line number Diff line number Diff line
@@ -680,7 +680,7 @@ handle_signal(struct ksignal *ksig, struct pt_regs *regs) 
		 * Ensure the signal handler starts with the new fpu state.

		 */

		if (used_math())

			drop_init_fpu(current);

			fpu_reset_state(current);

	}

	signal_setup_done(failed, ksig, test_thread_flag(TIF_SINGLESTEP));

}

arch/x86/kernel/traps.c

+2 −2
Original line number Diff line number Diff line
@@ -731,7 +731,7 @@ static void math_error(struct pt_regs *regs, int error_code, int trapnr) 
	/*

	 * Save the info for the exception handler and clear the error.

	 */

	save_init_fpu(task);

	unlazy_fpu(task);

	task->thread.trap_nr = trapnr;

	task->thread.error_code = error_code;

	info.si_signo = SIGFPE;
@@ -860,7 +860,7 @@ void math_state_restore(void) 
	kernel_fpu_disable();

	__thread_fpu_begin(tsk);

	if (unlikely(restore_fpu_checking(tsk))) {

		drop_init_fpu(tsk);

		fpu_reset_state(tsk);

		force_sig_info(SIGSEGV, SEND_SIG_PRIV, tsk);

	} else {

		tsk->thread.fpu_counter++;