linux-kernel - [tip:x86/fpu] x86/fpu: Make XSAVE check the base CPUID features before enabling

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Date:   Tue, 17 Oct 2017 09:23:14 -0700
From:   tip-bot for Andi Kleen <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     peterz@...radead.org, linux-kernel@...r.kernel.org,
        torvalds@...ux-foundation.org, hpa@...or.com, mingo@...nel.org,
        ak@...ux.intel.com, tglx@...utronix.de
Subject: [tip:x86/fpu] x86/fpu: Make XSAVE check the base CPUID features
 before enabling

Commit-ID:  ccb18db2ab9d923df07e7495123fe5fb02329713
Gitweb:     https://git.kernel.org/tip/ccb18db2ab9d923df07e7495123fe5fb02329713
Author:     Andi Kleen <ak@...ux.intel.com>
AuthorDate: Fri, 13 Oct 2017 14:56:44 -0700
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Tue, 17 Oct 2017 17:14:57 +0200

x86/fpu: Make XSAVE check the base CPUID features before enabling

Before enabling XSAVE, not only check the XSAVE specific CPUID bits,
but also the base CPUID features of the respective XSAVE feature.
This allows to disable individual XSAVE states using the existing
clearcpuid= option, which can be useful for performance testing
and debugging, and also in general avoids inconsistencies.

Signed-off-by: Andi Kleen <ak@...ux.intel.com>
Reviewed-by: Thomas Gleixner <tglx@...utronix.de>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Link: http://lkml.kernel.org/r/20171013215645.23166-5-andi@firstfloor.org
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/kernel/fpu/xstate.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index f1d5476..fb58129 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -15,6 +15,7 @@
 #include <asm/fpu/xstate.h>
 
 #include <asm/tlbflush.h>
+#include <asm/cpufeature.h>
 
 /*
  * Although we spell it out in here, the Processor Trace
@@ -36,6 +37,19 @@ static const char *xfeature_names[] =
 	"unknown xstate feature"	,
 };
 
+static short xsave_cpuid_features[] __initdata = {
+	X86_FEATURE_FPU,
+	X86_FEATURE_XMM,
+	X86_FEATURE_AVX,
+	X86_FEATURE_MPX,
+	X86_FEATURE_MPX,
+	X86_FEATURE_AVX512F,
+	X86_FEATURE_AVX512F,
+	X86_FEATURE_AVX512F,
+	X86_FEATURE_INTEL_PT,
+	X86_FEATURE_PKU,
+};
+
 /*
  * Mask of xstate features supported by the CPU and the kernel:
  */
@@ -726,6 +740,7 @@ void __init fpu__init_system_xstate(void)
 	unsigned int eax, ebx, ecx, edx;
 	static int on_boot_cpu __initdata = 1;
 	int err;
+	int i;
 
 	WARN_ON_FPU(!on_boot_cpu);
 	on_boot_cpu = 0;
@@ -759,6 +774,14 @@ void __init fpu__init_system_xstate(void)
 		goto out_disable;
 	}
 
+	/*
+	 * Clear XSAVE features that are disabled in the normal CPUID.
+	 */
+	for (i = 0; i < ARRAY_SIZE(xsave_cpuid_features); i++) {
+		if (!boot_cpu_has(xsave_cpuid_features[i]))
+			xfeatures_mask &= ~BIT(i);
+	}
+
 	xfeatures_mask &= fpu__get_supported_xfeatures_mask();
 
 	/* Enable xstate instructions to be able to continue with initialization: */