From c9ad488289144ae5ef53b012e15895ef1f5e4bb6 Mon Sep 17 00:00:00 2001 From: Avi Kivity Date: Thu, 6 May 2010 11:45:45 +0300 Subject: [PATCH] x86: Eliminate TS_XSAVE The fpu code currently uses current->thread_info->status & TS_XSAVE as a way to distinguish between XSAVE capable processors and older processors. The decision is not really task specific; instead we use the task status to avoid a global memory reference - the value should be the same across all threads. Eliminate this tie-in into the task structure by using an alternative instruction keyed off the XSAVE cpu feature; this results in shorter and faster code, without introducing a global memory reference. [ hpa: in the future, this probably should use an asm jmp ] Signed-off-by: Avi Kivity Acked-by: Suresh Siddha LKML-Reference: <1273135546-29690-2-git-send-email-avi@redhat.com> Signed-off-by: H. Peter Anvin --- arch/x86/include/asm/i387.h | 20 ++++++++++++++++---- arch/x86/include/asm/thread_info.h | 1 - arch/x86/kernel/cpu/common.c | 5 +---- arch/x86/kernel/i387.c | 5 +---- arch/x86/kernel/xsave.c | 6 +++--- 5 files changed, 21 insertions(+), 16 deletions(-) diff --git a/arch/x86/include/asm/i387.h b/arch/x86/include/asm/i387.h index da2930924501..a301a6825c3a 100644 --- a/arch/x86/include/asm/i387.h +++ b/arch/x86/include/asm/i387.h @@ -56,6 +56,18 @@ extern int restore_i387_xstate_ia32(void __user *buf); #define X87_FSW_ES (1 << 7) /* Exception Summary */ +static inline bool use_xsave(void) +{ + u8 has_xsave; + + alternative_io("mov $0, %0", + "mov $1, %0", + X86_FEATURE_XSAVE, + "=g"(has_xsave)); + + return has_xsave; +} + #ifdef CONFIG_X86_64 /* Ignore delayed exceptions from user space */ @@ -99,7 +111,7 @@ static inline void clear_fpu_state(struct task_struct *tsk) /* * xsave header may indicate the init state of the FP. */ - if ((task_thread_info(tsk)->status & TS_XSAVE) && + if (use_xsave() && !(xstate->xsave_hdr.xstate_bv & XSTATE_FP)) return; @@ -164,7 +176,7 @@ static inline void fxsave(struct task_struct *tsk) static inline void __save_init_fpu(struct task_struct *tsk) { - if (task_thread_info(tsk)->status & TS_XSAVE) + if (use_xsave()) xsave(tsk); else fxsave(tsk); @@ -218,7 +230,7 @@ static inline int fxrstor_checking(struct i387_fxsave_struct *fx) */ static inline void __save_init_fpu(struct task_struct *tsk) { - if (task_thread_info(tsk)->status & TS_XSAVE) { + if (use_xsave()) { struct xsave_struct *xstate = &tsk->thread.xstate->xsave; struct i387_fxsave_struct *fx = &tsk->thread.xstate->fxsave; @@ -266,7 +278,7 @@ end: static inline int restore_fpu_checking(struct task_struct *tsk) { - if (task_thread_info(tsk)->status & TS_XSAVE) + if (use_xsave()) return xrstor_checking(&tsk->thread.xstate->xsave); else return fxrstor_checking(&tsk->thread.xstate->fxsave); diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h index e0d28901e969..e9e341505ab3 100644 --- a/arch/x86/include/asm/thread_info.h +++ b/arch/x86/include/asm/thread_info.h @@ -244,7 +244,6 @@ static inline struct thread_info *current_thread_info(void) #define TS_POLLING 0x0004 /* true if in idle loop and not sleeping */ #define TS_RESTORE_SIGMASK 0x0008 /* restore signal mask in do_signal() */ -#define TS_XSAVE 0x0010 /* Use xsave/xrstor */ #define tsk_is_polling(t) (task_thread_info(t)->status & TS_POLLING) diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 4868e4a951ee..c1c00d0b1692 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -1243,10 +1243,7 @@ void __cpuinit cpu_init(void) /* * Force FPU initialization: */ - if (cpu_has_xsave) - current_thread_info()->status = TS_XSAVE; - else - current_thread_info()->status = 0; + current_thread_info()->status = 0; clear_used_math(); mxcsr_feature_mask_init(); diff --git a/arch/x86/kernel/i387.c b/arch/x86/kernel/i387.c index 54c31c285488..14ca1dc7a703 100644 --- a/arch/x86/kernel/i387.c +++ b/arch/x86/kernel/i387.c @@ -102,10 +102,7 @@ void __cpuinit fpu_init(void) mxcsr_feature_mask_init(); /* clean state in init */ - if (cpu_has_xsave) - current_thread_info()->status = TS_XSAVE; - else - current_thread_info()->status = 0; + current_thread_info()->status = 0; clear_used_math(); } #endif /* CONFIG_X86_64 */ diff --git a/arch/x86/kernel/xsave.c b/arch/x86/kernel/xsave.c index 782c3a362ec6..c1b0a11033a2 100644 --- a/arch/x86/kernel/xsave.c +++ b/arch/x86/kernel/xsave.c @@ -99,7 +99,7 @@ int save_i387_xstate(void __user *buf) if (err) return err; - if (task_thread_info(tsk)->status & TS_XSAVE) + if (use_xsave()) err = xsave_user(buf); else err = fxsave_user(buf); @@ -116,7 +116,7 @@ int save_i387_xstate(void __user *buf) clear_used_math(); /* trigger finit */ - if (task_thread_info(tsk)->status & TS_XSAVE) { + if (use_xsave()) { struct _fpstate __user *fx = buf; struct _xstate __user *x = buf; u64 xstate_bv; @@ -225,7 +225,7 @@ int restore_i387_xstate(void __user *buf) clts(); task_thread_info(current)->status |= TS_USEDFPU; } - if (task_thread_info(tsk)->status & TS_XSAVE) + if (use_xsave()) err = restore_user_xstate(buf); else err = fxrstor_checking((__force struct i387_fxsave_struct *)