Messages in this thread Patch in this message | | | Date | Fri, 11 Mar 2016 12:32:06 +0100 | From | Borislav Petkov <> | Subject | [PATCH] x86/FPU: Fix FPU handling on legacy FPU machines |
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486 cores like Intel Quark support only the very old, legacy x87 FPU (FSAVE/FRSTOR, CPUID bit FXSR is not set). And our FPU code wasn't handling the saving and restoring there properly. First, Andy Shevchenko reported a splat:
WARNING: CPU: 0 PID: 823 at arch/x86/include/asm/fpu/internal.h:163 fpu__clear+0x8c/0x160
which was us trying to execute FXRSTOR on those machines even though they don't support it.
After taking care of that, Bryan O'Donoghue reported that a simple FPU test still failed because we weren't initializing the FPU state properly on those machines.
Take care of all that.
Reported-by: Andy Shevchenko <andy.shevchenko@gmail.com> Reported-and-tested-by: Bryan O'Donoghue <pure.logic@nexus-software.ie> Signed-off-by: Borislav Petkov <bp@suse.de> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Brian Gerst <brgerst@gmail.com> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> --- arch/x86/kernel/fpu/core.c | 4 +++- arch/x86/kernel/fpu/init.c | 2 +- 2 files changed, 4 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c index dea8e76d60c6..8e37cc8a539a 100644 --- a/arch/x86/kernel/fpu/core.c +++ b/arch/x86/kernel/fpu/core.c @@ -474,8 +474,10 @@ static inline void copy_init_fpstate_to_fpregs(void) { if (use_xsave()) copy_kernel_to_xregs(&init_fpstate.xsave, -1); - else + else if (static_cpu_has(X86_FEATURE_FXSR)) copy_kernel_to_fxregs(&init_fpstate.fxsave); + else + copy_kernel_to_fregs(&init_fpstate.fsave); } /* diff --git a/arch/x86/kernel/fpu/init.c b/arch/x86/kernel/fpu/init.c index e12cc0ad368e..c835f61d5feb 100644 --- a/arch/x86/kernel/fpu/init.c +++ b/arch/x86/kernel/fpu/init.c @@ -134,7 +134,7 @@ static void __init fpu__init_system_generic(void) * Set up the legacy init FPU context. (xstate init might overwrite this * with a more modern format, if the CPU supports it.) */ - fpstate_init_fxstate(&init_fpstate.fxsave); + fpstate_init(&init_fpstate); fpu__init_system_mxcsr(); } -- 2.3.5
-- Regards/Gruss, Boris.
ECO tip #101: Trim your mails when you reply.
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