On Tue, 18 Dec 2018, Aubrey Li wrote: > diff --git a/arch/x86/include/asm/fpu/internal.h > b/arch/x86/include/asm/fpu/internal.h > index a38bf5a1e37a..8778ac172255 100644 > --- a/arch/x86/include/asm/fpu/internal.h > +++ b/arch/x86/include/asm/fpu/internal.h > @@ -411,6 +411,13 @@ static inline int copy_fpregs_to_fpstate(struct fpu *fpu) > { > if (likely(use_xsave())) { > copy_xregs_to_kernel(&fpu->state.xsave); > + > + /* > + * AVX512 state is tracked here because its use is > + * known to slow the max clock speed of the core. > + */ > + if (fpu->state.xsave.header.xfeatures & XFEATURE_MASK_AVX512) > + fpu->avx512_timestamp = jiffies_64;
Even if unlikely this is incorrect when running a 32 bit kernel because there jiffies_64 cannot be atomically loaded vs. a concurrent update. See the comment in include/linux/jiffies.h right above the jiffies_64 declaration. Thanks, tglx