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authorH.J. Lu <hjl.tools@gmail.com>2013-07-26 18:11:56 +0200
committerH. Peter Anvin <hpa@linux.intel.com>2013-07-26 18:11:56 +0200
commiteaa5a990191d204ba0f9d35dbe5505ec2cdd1460 (patch)
treec6ccf3fffc6f575e322ba84ed1de80cda14f49a3 /arch/x86/kernel
parentx86/iommu/vt-d: Expand interrupt remapping quirk to cover x58 chipset (diff)
downloadlinux-eaa5a990191d204ba0f9d35dbe5505ec2cdd1460.tar.xz
linux-eaa5a990191d204ba0f9d35dbe5505ec2cdd1460.zip
x86, fpu: correct the asm constraints for fxsave, unbreak mxcsr.daz
GCC will optimize mxcsr_feature_mask_init in arch/x86/kernel/i387.c: memset(&fx_scratch, 0, sizeof(struct i387_fxsave_struct)); asm volatile("fxsave %0" : : "m" (fx_scratch)); mask = fx_scratch.mxcsr_mask; if (mask == 0) mask = 0x0000ffbf; to memset(&fx_scratch, 0, sizeof(struct i387_fxsave_struct)); asm volatile("fxsave %0" : : "m" (fx_scratch)); mask = 0x0000ffbf; since asm statement doesn’t say it will update fx_scratch. As the result, the DAZ bit will be cleared. This patch fixes it. This bug dates back to at least kernel 2.6.12. Signed-off-by: H. Peter Anvin <hpa@linux.intel.com> Cc: <stable@vger.kernel.org>
Diffstat (limited to 'arch/x86/kernel')
-rw-r--r--arch/x86/kernel/i387.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/x86/kernel/i387.c b/arch/x86/kernel/i387.c
index 202d24f0f7e7..5d576ab34403 100644
--- a/arch/x86/kernel/i387.c
+++ b/arch/x86/kernel/i387.c
@@ -116,7 +116,7 @@ static void mxcsr_feature_mask_init(void)
if (cpu_has_fxsr) {
memset(&fx_scratch, 0, sizeof(struct i387_fxsave_struct));
- asm volatile("fxsave %0" : : "m" (fx_scratch));
+ asm volatile("fxsave %0" : "+m" (fx_scratch));
mask = fx_scratch.mxcsr_mask;
if (mask == 0)
mask = 0x0000ffbf;