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author | Suresh Siddha <suresh.b.siddha@intel.com> | 2008-07-29 19:29:20 +0200 |
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committer | Ingo Molnar <mingo@elte.hu> | 2008-07-30 19:49:24 +0200 |
commit | b359e8a434cc3d09847010fc4aeccf48d69740e4 (patch) | |
tree | 8911c299dc1768c78d5452a1e7e0efd2fc8d5abb /include/asm-x86/i387.h | |
parent | x86, xsave: enable xsave/xrstor on cpus with xsave support (diff) | |
download | linux-b359e8a434cc3d09847010fc4aeccf48d69740e4.tar.xz linux-b359e8a434cc3d09847010fc4aeccf48d69740e4.zip |
x86, xsave: context switch support using xsave/xrstor
Uses xsave/xrstor (instead of traditional fxsave/fxrstor) in context switch
when available.
Introduces TS_XSAVE flag, which determine the need to use xsave/xrstor
instructions during context switch instead of the legacy fxsave/fxrstor
instructions. Thread-synchronous status word is already in L1 cache during
this code patch and thus minimizes the performance penality compared to
(cpu_has_xsave) checks.
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'include/asm-x86/i387.h')
-rw-r--r-- | include/asm-x86/i387.h | 64 |
1 files changed, 59 insertions, 5 deletions
diff --git a/include/asm-x86/i387.h b/include/asm-x86/i387.h index 6a6647896670..a6d256f4ac81 100644 --- a/include/asm-x86/i387.h +++ b/include/asm-x86/i387.h @@ -36,6 +36,8 @@ extern int save_i387_ia32(struct _fpstate_ia32 __user *buf); extern int restore_i387_ia32(struct _fpstate_ia32 __user *buf); #endif +#define X87_FSW_ES (1 << 7) /* Exception Summary */ + #ifdef CONFIG_X86_64 /* Ignore delayed exceptions from user space */ @@ -46,7 +48,7 @@ static inline void tolerant_fwait(void) _ASM_EXTABLE(1b, 2b)); } -static inline int restore_fpu_checking(struct i387_fxsave_struct *fx) +static inline int fxrstor_checking(struct i387_fxsave_struct *fx) { int err; @@ -66,15 +68,31 @@ static inline int restore_fpu_checking(struct i387_fxsave_struct *fx) return err; } -#define X87_FSW_ES (1 << 7) /* Exception Summary */ +static inline int restore_fpu_checking(struct task_struct *tsk) +{ + if (task_thread_info(tsk)->status & TS_XSAVE) + return xrstor_checking(&tsk->thread.xstate->xsave); + else + return fxrstor_checking(&tsk->thread.xstate->fxsave); +} /* AMD CPUs don't save/restore FDP/FIP/FOP unless an exception is pending. Clear the x87 state here by setting it to fixed values. The kernel data segment can be sometimes 0 and sometimes new user value. Both should be ok. Use the PDA as safe address because it should be already in L1. */ -static inline void clear_fpu_state(struct i387_fxsave_struct *fx) +static inline void clear_fpu_state(struct task_struct *tsk) { + struct xsave_struct *xstate = &tsk->thread.xstate->xsave; + struct i387_fxsave_struct *fx = &tsk->thread.xstate->fxsave; + + /* + * xsave header may indicate the init state of the FP. + */ + if ((task_thread_info(tsk)->status & TS_XSAVE) && + !(xstate->xsave_hdr.xstate_bv & XSTATE_FP)) + return; + if (unlikely(fx->swd & X87_FSW_ES)) asm volatile("fnclex"); alternative_input(ASM_NOP8 ASM_NOP2, @@ -107,7 +125,7 @@ static inline int save_i387_checking(struct i387_fxsave_struct __user *fx) return err; } -static inline void __save_init_fpu(struct task_struct *tsk) +static inline void fxsave(struct task_struct *tsk) { /* Using "rex64; fxsave %0" is broken because, if the memory operand uses any extended registers for addressing, a second REX prefix @@ -132,7 +150,16 @@ static inline void __save_init_fpu(struct task_struct *tsk) : "=m" (tsk->thread.xstate->fxsave) : "cdaSDb" (&tsk->thread.xstate->fxsave)); #endif - clear_fpu_state(&tsk->thread.xstate->fxsave); +} + +static inline void __save_init_fpu(struct task_struct *tsk) +{ + if (task_thread_info(tsk)->status & TS_XSAVE) + xsave(tsk); + else + fxsave(tsk); + + clear_fpu_state(tsk); task_thread_info(tsk)->status &= ~TS_USEDFPU; } @@ -147,6 +174,10 @@ static inline void tolerant_fwait(void) static inline void restore_fpu(struct task_struct *tsk) { + if (task_thread_info(tsk)->status & TS_XSAVE) { + xrstor_checking(&tsk->thread.xstate->xsave); + return; + } /* * The "nop" is needed to make the instructions the same * length. @@ -172,6 +203,27 @@ static inline void restore_fpu(struct task_struct *tsk) */ static inline void __save_init_fpu(struct task_struct *tsk) { + if (task_thread_info(tsk)->status & TS_XSAVE) { + struct xsave_struct *xstate = &tsk->thread.xstate->xsave; + struct i387_fxsave_struct *fx = &tsk->thread.xstate->fxsave; + + xsave(tsk); + + /* + * xsave header may indicate the init state of the FP. + */ + if (!(xstate->xsave_hdr.xstate_bv & XSTATE_FP)) + goto end; + + if (unlikely(fx->swd & X87_FSW_ES)) + asm volatile("fnclex"); + + /* + * we can do a simple return here or be paranoid :) + */ + goto clear_state; + } + /* Use more nops than strictly needed in case the compiler varies code */ alternative_input( @@ -181,6 +233,7 @@ static inline void __save_init_fpu(struct task_struct *tsk) X86_FEATURE_FXSR, [fx] "m" (tsk->thread.xstate->fxsave), [fsw] "m" (tsk->thread.xstate->fxsave.swd) : "memory"); +clear_state: /* 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. safe_address is a random variable that should be in L1 */ @@ -190,6 +243,7 @@ static inline void __save_init_fpu(struct task_struct *tsk) "fildl %[addr]", /* set F?P to defined value */ X86_FEATURE_FXSAVE_LEAK, [addr] "m" (safe_address)); +end: task_thread_info(tsk)->status &= ~TS_USEDFPU; } |