Messages in this thread | | | Date | Sat, 12 Mar 2016 16:08:09 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH] x86/FPU: Fix FPU handling on legacy FPU machines |
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* Linus Torvalds <torvalds@linux-foundation.org> wrote:
> On Fri, Mar 11, 2016 at 3:32 AM, Borislav Petkov <bp@alien8.de> wrote: > > 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. > > Obvious Ack to the patch, along with a "how did this ever work > before?" comment..
So the window for 'real' breakage was relatively short: this is an older bug but only became a serious bug with the following upcoming commit:
58122bf1d856 x86/fpu: Default eagerfpu=on on all CPUs
... but it's nice to have it fixed nevertheless!
Thanks,
Ingo
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