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 --- Index: tip-0728/arch/x86/kernel/cpu/common.c =================================================================== --- tip-0728.orig/arch/x86/kernel/cpu/common.c 2008-07-28 18:23:14.000000000 -0700 +++ tip-0728/arch/x86/kernel/cpu/common.c 2008-07-28 18:27:28.000000000 -0700 @@ -709,7 +709,10 @@ /* * Force FPU initialization: */ - current_thread_info()->status = 0; + if (cpu_has_xsave) + current_thread_info()->status = TS_XSAVE; + else + current_thread_info()->status = 0; clear_used_math(); mxcsr_feature_mask_init(); Index: tip-0728/arch/x86/kernel/i387.c =================================================================== --- tip-0728.orig/arch/x86/kernel/i387.c 2008-07-28 18:23:45.000000000 -0700 +++ tip-0728/arch/x86/kernel/i387.c 2008-07-28 18:27:28.000000000 -0700 @@ -97,7 +97,10 @@ mxcsr_feature_mask_init(); /* clean state in init */ - current_thread_info()->status = 0; + if (cpu_has_xsave) + current_thread_info()->status = TS_XSAVE; + else + current_thread_info()->status = 0; clear_used_math(); } #endif /* CONFIG_X86_64 */ Index: tip-0728/include/asm-x86/i387.h =================================================================== --- tip-0728.orig/include/asm-x86/i387.h 2008-07-28 18:23:14.000000000 -0700 +++ tip-0728/include/asm-x86/i387.h 2008-07-28 18:27:28.000000000 -0700 @@ -37,6 +37,8 @@ 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 */ @@ -47,7 +49,7 @@ _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; @@ -67,15 +69,31 @@ 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, @@ -108,7 +126,7 @@ 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 @@ -133,7 +151,16 @@ : "=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; } @@ -148,6 +175,10 @@ 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. @@ -173,6 +204,27 @@ */ 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( @@ -182,6 +234,7 @@ 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 */ @@ -191,6 +244,7 @@ "fildl %[addr]", /* set F?P to defined value */ X86_FEATURE_FXSAVE_LEAK, [addr] "m" (safe_address)); +end: task_thread_info(tsk)->status &= ~TS_USEDFPU; } Index: tip-0728/include/asm-x86/processor.h =================================================================== --- tip-0728.orig/include/asm-x86/processor.h 2008-07-28 18:23:14.000000000 -0700 +++ tip-0728/include/asm-x86/processor.h 2008-07-28 18:27:28.000000000 -0700 @@ -367,6 +367,7 @@ struct i387_fsave_struct fsave; struct i387_fxsave_struct fxsave; struct i387_soft_struct soft; + struct xsave_struct xsave; }; #ifdef CONFIG_X86_64 Index: tip-0728/include/asm-x86/thread_info.h =================================================================== --- tip-0728.orig/include/asm-x86/thread_info.h 2008-07-28 18:20:15.000000000 -0700 +++ tip-0728/include/asm-x86/thread_info.h 2008-07-28 18:27:28.000000000 -0700 @@ -241,6 +241,7 @@ #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) Index: tip-0728/include/asm-x86/xsave.h =================================================================== --- tip-0728.orig/include/asm-x86/xsave.h 2008-07-28 18:23:14.000000000 -0700 +++ tip-0728/include/asm-x86/xsave.h 2008-07-28 18:27:28.000000000 -0700 @@ -17,10 +17,43 @@ #define XCNTXT_LMASK (XSTATE_FP | XSTATE_SSE) #define XCNTXT_HMASK 0x0 +#ifdef CONFIG_X86_64 +#define REX_PREFIX "0x48, " +#else +#define REX_PREFIX +#endif + extern unsigned int xstate_size, pcntxt_hmask, pcntxt_lmask; extern struct xsave_struct *init_xstate_buf; extern void xsave_cntxt_init(void); extern void xsave_init(void); +extern int init_fpu(struct task_struct *child); + +static inline int xrstor_checking(struct xsave_struct *fx) +{ + int err; + + asm volatile("1: .byte " REX_PREFIX "0x0f,0xae,0x2f\n\t" + "2:\n" + ".section .fixup,\"ax\"\n" + "3: movl $-1,%[err]\n" + " jmp 2b\n" + ".previous\n" + _ASM_EXTABLE(1b, 3b) + : [err] "=r" (err) + : "D" (fx), "m" (*fx), "a" (-1), "d" (-1), "0" (0) + : "memory"); + + return err; +} +static inline void xsave(struct task_struct *tsk) +{ + /* This, however, we can work around by forcing the compiler to select + an addressing mode that doesn't require extended registers. */ + __asm__ __volatile__(".byte " REX_PREFIX "0x0f,0xae,0x27" + ::"D" (&(tsk->thread.xstate->xsave)), + "a" (-1), "d"(-1) : "memory"); +} #endif Index: tip-0728/arch/x86/kernel/traps_64.c =================================================================== --- tip-0728.orig/arch/x86/kernel/traps_64.c 2008-07-28 18:23:14.000000000 -0700 +++ tip-0728/arch/x86/kernel/traps_64.c 2008-07-28 18:27:28.000000000 -0700 @@ -1147,7 +1147,7 @@ /* * Paranoid restore. send a SIGSEGV if we fail to restore the state. */ - if (unlikely(restore_fpu_checking(&me->thread.xstate->fxsave))) { + if (unlikely(restore_fpu_checking(me))) { stts(); force_sig(SIGSEGV, me); return; -- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/