diff options
| author | H.J. Lu <hjl.tools@gmail.com> | 2013-07-26 09:11:56 -0700 |
|---|---|---|
| committer | Ben Hutchings <ben@decadent.org.uk> | 2013-09-10 01:57:14 +0100 |
| commit | 708d8db1f9265dbc239338a26202fd2099b72337 (patch) | |
| tree | 16e10f96732b75884a20bd0825f9b6b0a2106bd7 /arch/x86 | |
| parent | 2c8efb72eb19898e2ff31184c76e37a0070c494b (diff) | |
x86, fpu: correct the asm constraints for fxsave, unbreak mxcsr.daz
commit eaa5a990191d204ba0f9d35dbe5505ec2cdd1460 upstream.
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>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Diffstat (limited to 'arch/x86')
| -rw-r--r-- | arch/x86/kernel/i387.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/x86/kernel/i387.c b/arch/x86/kernel/i387.c index 739d8598f789..fa4ea0995937 100644 --- a/arch/x86/kernel/i387.c +++ b/arch/x86/kernel/i387.c @@ -51,7 +51,7 @@ void __cpuinit mxcsr_feature_mask_init(void) clts(); 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; |