mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-10-03 23:58:05 +00:00
7575637ab2
math_state_restore() can race with kernel_fpu_begin() if irq comes right after __thread_fpu_begin(), __save_init_fpu() will overwrite fpu->state we are going to restore. Add 2 simple helpers, kernel_fpu_disable() and kernel_fpu_enable() which simply set/clear in_kernel_fpu, and change math_state_restore() to exclude kernel_fpu_begin() in between. Alternatively we could use local_irq_save/restore, but probably these new helpers can have more users. Perhaps they should disable/enable preemption themselves, in this case we can remove preempt_disable() in __restore_xstate_sig(). Signed-off-by: Oleg Nesterov <oleg@redhat.com> Reviewed-by: Rik van Riel <riel@redhat.com> Cc: matt.fleming@intel.com Cc: bp@suse.de Cc: pbonzini@redhat.com Cc: luto@amacapital.net Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Suresh Siddha <sbsiddha@gmail.com> Link: http://lkml.kernel.org/r/20150115192028.GD27332@redhat.com Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
108 lines
2.7 KiB
C
108 lines
2.7 KiB
C
/*
|
|
* Copyright (C) 1994 Linus Torvalds
|
|
*
|
|
* Pentium III FXSR, SSE support
|
|
* General FPU state handling cleanups
|
|
* Gareth Hughes <gareth@valinux.com>, May 2000
|
|
* x86-64 work by Andi Kleen 2002
|
|
*/
|
|
|
|
#ifndef _ASM_X86_I387_H
|
|
#define _ASM_X86_I387_H
|
|
|
|
#ifndef __ASSEMBLY__
|
|
|
|
#include <linux/sched.h>
|
|
#include <linux/hardirq.h>
|
|
|
|
struct pt_regs;
|
|
struct user_i387_struct;
|
|
|
|
extern int init_fpu(struct task_struct *child);
|
|
extern void fpu_finit(struct fpu *fpu);
|
|
extern int dump_fpu(struct pt_regs *, struct user_i387_struct *);
|
|
extern void math_state_restore(void);
|
|
|
|
extern bool irq_fpu_usable(void);
|
|
|
|
/*
|
|
* Careful: __kernel_fpu_begin/end() must be called with preempt disabled
|
|
* and they don't touch the preempt state on their own.
|
|
* If you enable preemption after __kernel_fpu_begin(), preempt notifier
|
|
* should call the __kernel_fpu_end() to prevent the kernel/user FPU
|
|
* state from getting corrupted. KVM for example uses this model.
|
|
*
|
|
* All other cases use kernel_fpu_begin/end() which disable preemption
|
|
* during kernel FPU usage.
|
|
*/
|
|
extern void __kernel_fpu_begin(void);
|
|
extern void __kernel_fpu_end(void);
|
|
|
|
static inline void kernel_fpu_begin(void)
|
|
{
|
|
preempt_disable();
|
|
WARN_ON_ONCE(!irq_fpu_usable());
|
|
__kernel_fpu_begin();
|
|
}
|
|
|
|
static inline void kernel_fpu_end(void)
|
|
{
|
|
__kernel_fpu_end();
|
|
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
|
|
* get used from interrupt context as well. To prevent these kernel instructions
|
|
* in interrupt context interacting wrongly with other user/kernel fpu usage, we
|
|
* should use them only in the context of irq_ts_save/restore()
|
|
*/
|
|
static inline int irq_ts_save(void)
|
|
{
|
|
/*
|
|
* If in process context and not atomic, we can take a spurious DNA fault.
|
|
* Otherwise, doing clts() in process context requires disabling preemption
|
|
* or some heavy lifting like kernel_fpu_begin()
|
|
*/
|
|
if (!in_atomic())
|
|
return 0;
|
|
|
|
if (read_cr0() & X86_CR0_TS) {
|
|
clts();
|
|
return 1;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
static inline void irq_ts_restore(int TS_state)
|
|
{
|
|
if (TS_state)
|
|
stts();
|
|
}
|
|
|
|
/*
|
|
* The question "does this thread have fpu access?"
|
|
* is slightly racy, since preemption could come in
|
|
* and revoke it immediately after the test.
|
|
*
|
|
* However, even in that very unlikely scenario,
|
|
* we can just assume we have FPU access - typically
|
|
* to save the FP state - we'll just take a #NM
|
|
* fault and get the FPU access back.
|
|
*/
|
|
static inline int user_has_fpu(void)
|
|
{
|
|
return current->thread.fpu.has_fpu;
|
|
}
|
|
|
|
extern void unlazy_fpu(struct task_struct *tsk);
|
|
|
|
#endif /* __ASSEMBLY__ */
|
|
|
|
#endif /* _ASM_X86_I387_H */
|