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Commit c93eceda 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 updates from Ingo Molnar:
 "Initial round of kernel_fpu_begin/end cleanups from Oleg Nesterov,
  plus a cleanup from Borislav Petkov"

* 'x86-fpu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86, fpu: Fix math_state_restore() race with kernel_fpu_begin()
  x86, fpu: Don't abuse has_fpu in __kernel_fpu_begin/end()
  x86, fpu: Introduce per-cpu in_kernel_fpu state
  x86/fpu: Use a symbolic name for asm operand
parents 072bc448 7575637a

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

+6 −4
Original line number Diff line number Diff line
@@ -207,7 +207,7 @@ static inline void fpu_fxsave(struct fpu *fpu) 
	if (config_enabled(CONFIG_X86_32))

		asm volatile( "fxsave %[fx]" : [fx] "=m" (fpu->state->fxsave));

	else if (config_enabled(CONFIG_AS_FXSAVEQ))

		asm volatile("fxsaveq %0" : "=m" (fpu->state->fxsave));

		asm volatile("fxsaveq %[fx]" : [fx] "=m" (fpu->state->fxsave));

	else {

		/* Using "rex64; fxsave %0" is broken because, if the memory

		 * operand uses any extended registers for addressing, a second
@@ -290,9 +290,11 @@ static inline int fpu_restore_checking(struct fpu *fpu) 


static inline int restore_fpu_checking(struct task_struct *tsk)

{

	/* AMD K7/K8 CPUs don't save/restore FDP/FIP/FOP unless an exception

	   is pending.  Clear the x87 state here by setting it to fixed

	   values. "m" is a random variable that should be in L1 */

	/*

	 * AMD K7/K8 CPUs don't save/restore FDP/FIP/FOP unless an exception is

	 * pending. Clear the x87 state here by setting it to fixed values.

	 * "m" is a random variable that should be in L1.

	 */

	if (unlikely(static_cpu_has_bug_safe(X86_BUG_FXSAVE_LEAK))) {

		asm volatile(

			"fnclex\n\t"

arch/x86/include/asm/i387.h

+5 −1
Original line number Diff line number Diff line
@@ -40,8 +40,8 @@ extern void __kernel_fpu_end(void); 


static inline void kernel_fpu_begin(void)

{

	WARN_ON_ONCE(!irq_fpu_usable());

	preempt_disable();

	WARN_ON_ONCE(!irq_fpu_usable());

	__kernel_fpu_begin();

}
@@ -51,6 +51,10 @@ static inline void kernel_fpu_end(void) 
	preempt_enable();

}



/* Must be called with preempt disabled */

extern void kernel_fpu_disable(void);

extern void kernel_fpu_enable(void);



/*

 * Some instructions like VIA's padlock instructions generate a spurious

 * DNA fault but don't modify SSE registers. And these instructions

arch/x86/kernel/i387.c

+26 −13
Original line number Diff line number Diff line
@@ -19,6 +19,19 @@ 
#include <asm/fpu-internal.h>

#include <asm/user.h>



static DEFINE_PER_CPU(bool, in_kernel_fpu);



void kernel_fpu_disable(void)

{

	WARN_ON(this_cpu_read(in_kernel_fpu));

	this_cpu_write(in_kernel_fpu, true);

}



void kernel_fpu_enable(void)

{

	this_cpu_write(in_kernel_fpu, false);

}



/*

 * Were we in an interrupt that interrupted kernel mode?

 *
@@ -33,6 +46,9 @@ 
 */

static inline bool interrupted_kernel_fpu_idle(void)

{

	if (this_cpu_read(in_kernel_fpu))

		return false;



	if (use_eager_fpu())

		return __thread_has_fpu(current);
@@ -73,10 +89,10 @@ void __kernel_fpu_begin(void) 
{

	struct task_struct *me = current;



	this_cpu_write(in_kernel_fpu, true);



	if (__thread_has_fpu(me)) {

		__thread_clear_has_fpu(me);

		__save_init_fpu(me);

		/* We do 'stts()' in __kernel_fpu_end() */

	} else if (!use_eager_fpu()) {

		this_cpu_write(fpu_owner_task, NULL);

		clts();
@@ -86,19 +102,16 @@ EXPORT_SYMBOL(__kernel_fpu_begin); 


void __kernel_fpu_end(void)

{

	if (use_eager_fpu()) {

		/*

		 * For eager fpu, most the time, tsk_used_math() is true.

		 * Restore the user math as we are done with the kernel usage.

		 * At few instances during thread exit, signal handling etc,

		 * tsk_used_math() is false. Those few places will take proper

		 * actions, so we don't need to restore the math here.

		 */

		if (likely(tsk_used_math(current)))

			math_state_restore();

	} else {

	struct task_struct *me = current;



	if (__thread_has_fpu(me)) {

		if (WARN_ON(restore_fpu_checking(me)))

			drop_init_fpu(me);

	} else if (!use_eager_fpu()) {

		stts();

	}



	this_cpu_write(in_kernel_fpu, false);

}

EXPORT_SYMBOL(__kernel_fpu_end);

arch/x86/kernel/traps.c

+5 −7
Original line number Diff line number Diff line
@@ -859,19 +859,17 @@ void math_state_restore(void) 
		local_irq_disable();

	}



	/* Avoid __kernel_fpu_begin() right after __thread_fpu_begin() */

	kernel_fpu_disable();

	__thread_fpu_begin(tsk);



	/*

	 * Paranoid restore. send a SIGSEGV if we fail to restore the state.

	 */

	if (unlikely(restore_fpu_checking(tsk))) {

		drop_init_fpu(tsk);

		force_sig_info(SIGSEGV, SEND_SIG_PRIV, tsk);

		return;

	}



	} else {

		tsk->thread.fpu_counter++;

	}

	kernel_fpu_enable();

}

EXPORT_SYMBOL_GPL(math_state_restore);



dotraplinkage void