xsaveopt is a more optimized form of xsave specifically designed for the context switch usage. xsaveopt doesn't save the state that's not modified from the prior xrstor. And if a specific feature state gets modified to the init state, then xsaveopt just updates the header bit in the xsave memory layout without updating the corresponding memory layout. Signed-off-by: Suresh Siddha --- arch/x86/include/asm/i387.h | 2 +- arch/x86/include/asm/xsave.h | 9 ++++++--- arch/x86/kernel/cpu/addon_cpuid_features.c | 1 + arch/x86/kernel/cpu/common.c | 8 ++++++++ 4 files changed, 16 insertions(+), 4 deletions(-) Index: tip-linux-2.6/arch/x86/include/asm/xsave.h =================================================================== --- tip-linux-2.6.orig/arch/x86/include/asm/xsave.h +++ tip-linux-2.6/arch/x86/include/asm/xsave.h @@ -135,8 +135,11 @@ static inline void fpu_xsave(struct fpu { /* 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" (&(fpu->state->xsave)), - "a" (-1), "d"(-1) : "memory"); + alternative_input( + ".byte " REX_PREFIX "0x0f,0xae,0x27", + ".byte " REX_PREFIX "0x0f,0xae,0x37", + X86_FEATURE_XSAVEOPT, + [fx] "D" (&fpu->state->xsave), "a" (-1), "d" (-1) : + "memory"); } #endif Index: tip-linux-2.6/arch/x86/kernel/cpu/common.c =================================================================== --- tip-linux-2.6.orig/arch/x86/kernel/cpu/common.c +++ tip-linux-2.6/arch/x86/kernel/cpu/common.c @@ -140,10 +140,18 @@ EXPORT_PER_CPU_SYMBOL_GPL(gdt_page); static int __init x86_xsave_setup(char *s) { setup_clear_cpu_cap(X86_FEATURE_XSAVE); + setup_clear_cpu_cap(X86_FEATURE_XSAVEOPT); return 1; } __setup("noxsave", x86_xsave_setup); +static int __init x86_xsaveopt_setup(char *s) +{ + setup_clear_cpu_cap(X86_FEATURE_XSAVEOPT); + return 1; +} +__setup("noxsaveopt", x86_xsaveopt_setup); + #ifdef CONFIG_X86_32 static int cachesize_override __cpuinitdata = -1; static int disable_x86_serial_nr __cpuinitdata = 1; Index: tip-linux-2.6/arch/x86/include/asm/i387.h =================================================================== --- tip-linux-2.6.orig/arch/x86/include/asm/i387.h +++ tip-linux-2.6/arch/x86/include/asm/i387.h @@ -60,7 +60,7 @@ extern int restore_i387_xstate_ia32(void static __always_inline __pure bool use_xsaveopt(void) { - return 0; + return static_cpu_has(X86_FEATURE_XSAVEOPT); } static __always_inline __pure bool use_xsave(void) Index: tip-linux-2.6/arch/x86/kernel/cpu/addon_cpuid_features.c =================================================================== --- tip-linux-2.6.orig/arch/x86/kernel/cpu/addon_cpuid_features.c +++ tip-linux-2.6/arch/x86/kernel/cpu/addon_cpuid_features.c @@ -35,6 +35,7 @@ void __cpuinit init_scattered_cpuid_feat { X86_FEATURE_ARAT, CR_EAX, 2, 0x00000006, 0 }, { X86_FEATURE_APERFMPERF, CR_ECX, 0, 0x00000006, 0 }, { X86_FEATURE_EPB, CR_ECX, 3, 0x00000006, 0 }, + { X86_FEATURE_XSAVEOPT, CR_EAX, 0, 0x0000000d, 1 }, { X86_FEATURE_CPB, CR_EDX, 9, 0x80000007, 0 }, { X86_FEATURE_NPT, CR_EDX, 0, 0x8000000a, 0 }, { X86_FEATURE_LBRV, CR_EDX, 1, 0x8000000a, 0 }, -- 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/