On Wed, Mar 09, 2016 at 05:57:39AM -0800, tip-bot for Andy Lutomirski wrote:
> Commit-ID: f363938c70a04e6bc99023a5e0c44ef7879b903f
> Gitweb: http://git.kernel.org/tip/f363938c70a04e6bc99023a5e0c44ef7879b903f
> Author: Andy Lutomirski <luto@xxxxxxxxxx>
> AuthorDate: Thu, 21 Jan 2016 15:24:31 -0800
> Committer: Ingo Molnar <mingo@xxxxxxxxxx>
> CommitDate: Wed, 9 Mar 2016 13:54:40 +0100
>
> x86/fpu: Fix 'no387' regression
>
> After fixing FPU option parsing, we now parse the 'no387' boot option
> too early: no387 clears X86_FEATURE_FPU before it's even probed, so
> the boot CPU promptly re-enables it.
>
> I suspect it gets even more confused on SMP.
>
> Fix the probing code to leave X86_FEATURE_FPU off if it's been
> disabled by setup_clear_cpu_cap().
...
> diff --git a/arch/x86/kernel/fpu/init.c b/arch/x86/kernel/fpu/init.c
> index 6d9f0a7..d53ab3d 100644
> --- a/arch/x86/kernel/fpu/init.c
> +++ b/arch/x86/kernel/fpu/init.c
> @@ -78,13 +78,15 @@ static void fpu__init_system_early_generic(struct cpuinfo_x86 *c)
> cr0 &= ~(X86_CR0_TS | X86_CR0_EM);
> write_cr0(cr0);
>
> - asm volatile("fninit ; fnstsw %0 ; fnstcw %1"
> - : "+m" (fsw), "+m" (fcw));
> + if (!test_bit(X86_FEATURE_FPU, (unsigned long *)cpu_caps_cleared)) {
> + asm volatile("fninit ; fnstsw %0 ; fnstcw %1"
> + : "+m" (fsw), "+m" (fcw));
I guess we should add another cpufeature interface to do that instead
of testing cpu_caps_cleared directly but I'll send that after the merge
window:
---
diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h
index 50e292a73a7b..63d7d0f5aa65 100644
--- a/arch/x86/include/asm/cpufeature.h
+++ b/arch/x86/include/asm/cpufeature.h
@@ -121,6 +121,10 @@ extern const char * const x86_bug_flags[NBUGINTS*32];
set_cpu_cap(&boot_cpu_data, bit); \
set_bit(bit, (unsigned long *)cpu_caps_set); \
} while (0)
+#define setup_cpu_feature_enabled(bit) \
+ cpu_feature_enabled(bit) && \
+ !test_bit(bit, (unsigned long *)cpu_caps_cleared) && \
+ test_bit(bit, (unsigned long *)cpu_caps_set)
#define cpu_has_fpu boot_cpu_has(X86_FEATURE_FPU)
#define cpu_has_pse boot_cpu_has(X86_FEATURE_PSE)
diff --git a/arch/x86/kernel/fpu/init.c b/arch/x86/kernel/fpu/init.c
index e12cc0ad368e..22dc03ddebe8 100644
--- a/arch/x86/kernel/fpu/init.c
+++ b/arch/x86/kernel/fpu/init.c
@@ -78,7 +78,7 @@ static void fpu__init_system_early_generic(struct cpuinfo_x86 *c)
cr0 &= ~(X86_CR0_TS | X86_CR0_EM);
write_cr0(cr0);
- if (!test_bit(X86_FEATURE_FPU, (unsigned long *)cpu_caps_cleared)) {
+ if (!setup_cpu_feature_enabled(X86_FEATURE_FPU)) {
asm volatile("fninit ; fnstsw %0 ; fnstcw %1"
: "+m" (fsw), "+m" (fcw));
--
Regards/Gruss,
Boris.
ECO tip #101: Trim your mails when you reply.
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