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 <suresh.b.siddha@intel.com>
---
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 },
--
