Commit-ID: eaa5a990191d204ba0f9d35dbe5505ec2cdd1460 Gitweb: http://git.kernel.org/tip/eaa5a990191d204ba0f9d35dbe5505ec2cdd1460 Author: H.J. Lu <hjl.tools@xxxxxxxxx> AuthorDate: Fri, 26 Jul 2013 09:11:56 -0700 Committer: H. Peter Anvin <hpa@xxxxxxxxxxxxxxx> CommitDate: Fri, 26 Jul 2013 09:11:56 -0700 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@xxxxxxxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> --- arch/x86/kernel/i387.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/kernel/i387.c b/arch/x86/kernel/i387.c index 202d24f..5d576ab 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; -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html