x86, fpu: enable eagerfpu by default for xsaveopt

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>

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 741d064..e8f7faa 100644 (file)
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -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

diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h
index 5dd2b47..0debdb5 100644 (file)
--- a/arch/x86/include/asm/cpufeature.h
+++ b/arch/x86/include/asm/cpufeature.h
@@ -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)

diff --git a/arch/x86/kernel/xsave.c b/arch/x86/kernel/xsave.c
index c0afd2c..e99f754 100644 (file)
--- a/arch/x86/kernel/xsave.c
+++ b/arch/x86/kernel/xsave.c
@@ -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);
 }