[PATCH v2 2/5] x86, fpu: enable eagerfpu by default for xsaveopt

From: Suresh Siddha
Date: Mon Sep 10 2012 - 14:12:58 EST

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@xxxxxxxxx>
Documentation/kernel-parameters.txt | 2 +-
arch/x86/include/asm/cpufeature.h | 1 +
arch/x86/kernel/xsave.c | 3 +++
3 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 6273099..b21bcbd 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1835,7 +1835,7 @@ 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
diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h
index eb9f8d1..36c2dc4 100644
--- a/arch/x86/include/asm/cpufeature.h
+++ b/arch/x86/include/asm/cpufeature.h
@@ -298,6 +298,7 @@ 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)
diff --git a/arch/x86/kernel/xsave.c b/arch/x86/kernel/xsave.c
index 66369f4..a447a7c 100644
--- a/arch/x86/kernel/xsave.c
+++ b/arch/x86/kernel/xsave.c
@@ -556,6 +556,9 @@ static void __init xstate_enable_boot_cpu(void)

+ 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);

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