linux-kernel - [PATCH 09/10] x86, xsave: check cpuid level for XSTATE

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Date:	Tue, 20 Jul 2010 20:50:56 +0200
From:	Robert Richter <robert.richter@....com>
To:	"H. Peter Anvin" <hpa@...or.com>
CC:	Ingo Molnar <mingo@...e.hu>,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Robert Richter <robert.richter@....com>
Subject: [PATCH 09/10] x86, xsave: check cpuid level for XSTATE_CPUID (0x0d)

The patch adds a check that tests if XSTATE_CPUID exists.

Signed-off-by: Robert Richter <robert.richter@....com>
---
 arch/x86/include/asm/xsave.h |    2 ++
 arch/x86/kernel/xsave.c      |    8 +++++++-
 2 files changed, 9 insertions(+), 1 deletions(-)

diff --git a/arch/x86/include/asm/xsave.h b/arch/x86/include/asm/xsave.h
index 4d3b5d1..d1b5f3a 100644
--- a/arch/x86/include/asm/xsave.h
+++ b/arch/x86/include/asm/xsave.h
@@ -4,6 +4,8 @@
 #include <linux/types.h>
 #include <asm/processor.h>
 
+#define XSTATE_CPUID		0x0000000d
+
 #define XSTATE_FP	0x1
 #define XSTATE_SSE	0x2
 #define XSTATE_YMM	0x4
diff --git a/arch/x86/kernel/xsave.c b/arch/x86/kernel/xsave.c
index 2322f58..49540b7 100644
--- a/arch/x86/kernel/xsave.c
+++ b/arch/x86/kernel/xsave.c
@@ -423,9 +423,15 @@ static void __init setup_xstate_init(void)
  */
 static void __cpuinit xstate_enable_boot_cpu(void)
 {
+	struct cpuinfo_x86 *c = &cpu_data(0);
 	unsigned int eax, ebx, ecx, edx;
 
-	cpuid_count(0xd, 0, &eax, &ebx, &ecx, &edx);
+	if (c->cpuid_level < XSTATE_CPUID) {
+		WARN(1, KERN_ERR "XSTATE_CPUID missing\n");
+		return;
+	}
+
+	cpuid_count(XSTATE_CPUID, 0, &eax, &ebx, &ecx, &edx);
 	pcntxt_mask = eax + ((u64)edx << 32);
 
 	if ((pcntxt_mask & XSTATE_FPSSE) != XSTATE_FPSSE) {
-- 
1.7.1.1


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