AuxXxilium/linux_dsm_epyc7002
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x86: split out core __math_state_restore

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Split the core fpu state restoration out into __math_state_restore, which
assumes that cr0.TS is clear and that the fpu context has been initialized.

This will be used during context switch.  There are two reasons this is
desireable:

- There's a small clarification.  When __switch_to() calls math_state_restore,
  it relies on the fact that tsk_used_math() returns true, and so will
  never do a blocking init_fpu().  __math_state_restore() does not have
  (or need) that logic, so the question never arises.

- It allows the clts() to be moved earler in __switch_to() so it can be performed
  while cpu context updates are batched (will be done in a later patch).

[ Impact: refactor code to make reuse cleaner; no functional change ]

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Alok Kataria <akataria@vmware.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
This commit is contained in:
Jeremy Fitzhardinge 2009-04-24 00:40:59 -07:00
parent 3fe0344faf
commit e6e9cac8c3
2 changed files with 24 additions and 10 deletions
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1
arch/x86/include/asm/i387.h
View File

@ -26,6 +26,7 @@ extern void fpu_init(void);
extern void mxcsr_feature_mask_init(void);
extern int init_fpu(struct task_struct *child);
extern asmlinkage void math_state_restore(void);
extern void __math_state_restore(void);
extern void init_thread_xstate(void);
extern int dump_fpu(struct pt_regs *, struct user_i387_struct *);

33
arch/x86/kernel/traps.c
View File

@ -813,6 +813,28 @@ asmlinkage void __attribute__((weak)) smp_threshold_interrupt(void)
{
}
/*
* __math_state_restore assumes that cr0.TS is already clear and the
* fpu state is all ready for use. Used during context switch.
*/
void __math_state_restore(void)
{
struct thread_info *thread = current_thread_info();
struct task_struct *tsk = thread->task;
/*
* Paranoid restore. send a SIGSEGV if we fail to restore the state.
*/
if (unlikely(restore_fpu_checking(tsk))) {
stts();
force_sig(SIGSEGV, tsk);
return;
}
thread->status |= TS_USEDFPU; /* So we fnsave on switch_to() */
tsk->fpu_counter++;
}
/*
* 'math_state_restore()' saves the current math information in the
* old math state array, and gets the new ones from the current task
@ -844,17 +866,8 @@ asmlinkage void math_state_restore(void)
}
clts(); /* Allow maths ops (or we recurse) */
/*
* Paranoid restore. send a SIGSEGV if we fail to restore the state.
*/
if (unlikely(restore_fpu_checking(tsk))) {
stts();
force_sig(SIGSEGV, tsk);
return;
}
thread->status |= TS_USEDFPU; /* So we fnsave on switch_to() */
tsk->fpu_counter++;
__math_state_restore();
}
EXPORT_SYMBOL_GPL(math_state_restore);