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authorAndy Lutomirski <luto@kernel.org>2016-01-24 14:38:06 -0800
committerIngo Molnar <mingo@kernel.org>2016-02-09 15:42:55 +0100
commit4ecd16ec7059390b430af34bd8bc3ca2b5dcef9a (patch)
treec48e855e5fe736567b2c70733896479066a82ce9 /arch/x86/include/asm/fpu
parent765bdb406de4b6132e349c5d4e077866536a9cc0 (diff)
x86/fpu: Fix math emulation in eager fpu mode
Systems without an FPU are generally old and therefore use lazy FPU switching. Unsurprisingly, math emulation in eager FPU mode is a bit buggy. Fix it. There were two bugs involving kernel code trying to use the FPU registers in eager mode even if they didn't exist and one BUG_ON() that was incorrect. Signed-off-by: Andy Lutomirski <luto@kernel.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Borislav Petkov <bp@alien8.de> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Fenghua Yu <fenghua.yu@intel.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Quentin Casasnovas <quentin.casasnovas@oracle.com> Cc: Rik van Riel <riel@redhat.com> Cc: Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: yu-cheng yu <yu-cheng.yu@intel.com> Link: http://lkml.kernel.org/r/b4b8d112436bd6fab866e1b4011131507e8d7fbe.1453675014.git.luto@kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/include/asm/fpu')
-rw-r--r--arch/x86/include/asm/fpu/internal.h3
1 files changed, 2 insertions, 1 deletions
diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h
index 0fd440df63f1..a1f78a9fbf41 100644
--- a/arch/x86/include/asm/fpu/internal.h
+++ b/arch/x86/include/asm/fpu/internal.h
@@ -589,7 +589,8 @@ switch_fpu_prepare(struct fpu *old_fpu, struct fpu *new_fpu, int cpu)
* If the task has used the math, pre-load the FPU on xsave processors
* or if the past 5 consecutive context-switches used math.
*/
- fpu.preload = new_fpu->fpstate_active &&
+ fpu.preload = static_cpu_has(X86_FEATURE_FPU) &&
+ new_fpu->fpstate_active &&
(use_eager_fpu() || new_fpu->counter > 5);
if (old_fpu->fpregs_active) {