to update AVX512 state
> + */
> +static inline void update_avx512_state(struct fpu *fpu)
> +{
> + /*
> + * AVX512 state is tracked here because its use is known to slow
> + * the max clock speed of the core.
> + *
> + * However, AVX512-using tasks are expected to clear this state when
> + * not actively using these registers. Thus, this tracking mechanism
> + * can miss. To ensure that false-negatives do not immediately show
> + * up, decay the usage count over time.
> + */
> + if (fpu->state.xsave.header.xfeatures & XFEATURE_MASK_AVX512)
> + fpu->avx512_usage = AVX512_STATE_DECAY_COUNT;
> + else if (fpu->avx512_usage)
> + fpu->avx512_usage--;
> +}
> +
> /*
> * This function is called only during boot time when x86 caps are not set
> * up and alternative can not be used yet.
> @@ -411,6 +432,7 @@ static inline int copy_fpregs_to_fpstate(struct fpu *fpu)
> {
> if (likely(use_xsave())) {
> copy_xregs_to_kernel(&fpu->state.xsave);
> + update_avx512_state(fpu);
> return 1;
> }
Is there a reason we shouldn't do:
if (!cpu_feature_enabled(X86_FEATURE_AVX512F))
update_avx512_state(fpu);
?
