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

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Date:	Mon, 10 Sep 2012 11:11:02 -0700
From:	Suresh Siddha <suresh.b.siddha@...el.com>
To:	hpa@...or.com, mingo@...nel.org, torvalds@...ux-foundation.org,
	andreas.herrmann3@....com, bp@...64.org, robert.richter@....com
Cc:	linux-kernel@...r.kernel.org,
	Suresh Siddha <suresh.b.siddha@...el.com>
Subject: [PATCH v2 2/5] 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@...el.com>
---
 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)
 	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);
 }
-- 
1.7.6.5

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