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x86, fpu: enable eagerfpu by default for xsaveopt

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xsaveopt/xrstor support optimized state save/restore by tracking the
INIT state and MODIFIED state during context-switch.

Enable eagerfpu by default for processors supporting xsaveopt.
Can be disabled by passing "eagerfpu=off" boot parameter.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Link: http://lkml.kernel.org/r/1347300665-6209-3-git-send-email-suresh.b.siddha@intel.com
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
This commit is contained in:
Suresh Siddha 2012-09-06 15:05:18 -07:00 committed by H. Peter Anvin
parent 5d2bd7009f
commit 212b02125f
3 changed files with 5 additions and 1 deletions
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2
Documentation/kernel-parameters.txt
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@ -1834,7 +1834,7 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
enabling legacy floating-point and sse state.
eagerfpu= [X86]
on enable eager fpu restore
on enable eager fpu restore (default for xsaveopt)
off disable eager fpu restore
nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or

1
arch/x86/include/asm/cpufeature.h
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@ -300,6 +300,7 @@ extern const char * const x86_power_flags[32];
#define cpu_has_xmm4_2 boot_cpu_has(X86_FEATURE_XMM4_2)
#define cpu_has_x2apic boot_cpu_has(X86_FEATURE_X2APIC)
#define cpu_has_xsave boot_cpu_has(X86_FEATURE_XSAVE)
#define cpu_has_xsaveopt boot_cpu_has(X86_FEATURE_XSAVEOPT)
#define cpu_has_osxsave boot_cpu_has(X86_FEATURE_OSXSAVE)
#define cpu_has_hypervisor boot_cpu_has(X86_FEATURE_HYPERVISOR)
#define cpu_has_pclmulqdq boot_cpu_has(X86_FEATURE_PCLMULQDQ)

3
arch/x86/kernel/xsave.c
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@ -557,6 +557,9 @@ static void __init xstate_enable_boot_cpu(void)
prepare_fx_sw_frame();
setup_init_fpu_buf();
if (cpu_has_xsaveopt && !disable_eagerfpu)
setup_force_cpu_cap(X86_FEATURE_EAGER_FPU);
pr_info("enabled xstate_bv 0x%llx, cntxt size 0x%x\n",
pcntxt_mask, xstate_size);
}