summary refs log tree commit diff
path: root/arch/x86
diff options
context:
space:
mode:
authorSuresh Siddha <suresh.b.siddha@intel.com>2009-12-16 16:25:42 -0800
committerH. Peter Anvin <hpa@zytor.com>2009-12-16 16:30:57 -0800
commit45a94d7cd45ed991914011919e7d40eb6d2546d1 (patch)
treee56674f1da20a6df352ea17f3242d03b2648e229 /arch/x86
parent6ede31e03084ee084bcee073ef3d1136f68d0906 (diff)
downloadlinux-45a94d7cd45ed991914011919e7d40eb6d2546d1.tar.gz
x86, cpuid: Add "volatile" to asm in native_cpuid()
xsave_cntxt_init() does something like:

	cpuid(0xd, ..);	// find out what features FP/SSE/.. etc are supported

	xsetbv();	// enable the features known to OS

	cpuid(0xd, ..);	// find out the size of the context for features enabled

Depending on what features get enabled in xsetbv(), value of the
cpuid.eax=0xd.ecx=0.ebx changes correspondingly (representing the
size of the context that is enabled).

As we don't have volatile keyword for native_cpuid(), gcc 4.1.2
optimizes away the second cpuid and the kernel continues to use
the cpuid information obtained before xsetbv(), ultimately leading to kernel
crash on processors supporting more state than the legacy FP/SSE.

Add "volatile" for native_cpuid().

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
LKML-Reference: <1261009542.2745.55.camel@sbs-t61.sc.intel.com>
Cc: stable@kernel.org
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Diffstat (limited to 'arch/x86')
-rw-r--r--arch/x86/include/asm/processor.h2
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 6f8ec1c37e0a..fc801bab1b3b 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -181,7 +181,7 @@ static inline void native_cpuid(unsigned int *eax, unsigned int *ebx,
 				unsigned int *ecx, unsigned int *edx)
 {
 	/* ecx is often an input as well as an output. */
-	asm("cpuid"
+	asm volatile("cpuid"
 	    : "=a" (*eax),
 	      "=b" (*ebx),
 	      "=c" (*ecx),