From 0fe4ff885f8a50082d9dc241b657472894caba16 Mon Sep 17 00:00:00 2001 From: Noah Goldstein Date: Tue, 16 Nov 2021 17:14:21 +0100 Subject: [PATCH] x86/fpu: Correct AVX512 state tracking Add a separate, local mask for tracking AVX512 usage which does not include the opmask xfeature set. Opmask registers usage does not cause frequency throttling so it is a completely unnecessary false positive. While at it, carve it out into a separate function to keep that abomination extracted out. [ bp: Rediff and cleanup ontop of 5.16-rc1. ] Signed-off-by: Noah Goldstein Signed-off-by: Borislav Petkov Link: https://lore.kernel.org/r/20210920053951.4093668-1-goldstein.w.n@gmail.com --- arch/x86/kernel/fpu/core.c | 21 ++++++++++++++------- 1 file changed, 14 insertions(+), 7 deletions(-) diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c index 8ea306b1bf8ec..dd3777ac0443f 100644 --- a/arch/x86/kernel/fpu/core.c +++ b/arch/x86/kernel/fpu/core.c @@ -98,6 +98,19 @@ bool irq_fpu_usable(void) } EXPORT_SYMBOL(irq_fpu_usable); +/* + * Track AVX512 state use because it is known to slow the max clock + * speed of the core. + */ +static void update_avx_timestamp(struct fpu *fpu) +{ + +#define AVX512_TRACKING_MASK (XFEATURE_MASK_ZMM_Hi256 | XFEATURE_MASK_Hi16_ZMM) + + if (fpu->fpstate->regs.xsave.header.xfeatures & AVX512_TRACKING_MASK) + fpu->avx512_timestamp = jiffies; +} + /* * Save the FPU register state in fpu->fpstate->regs. The register state is * preserved. @@ -116,13 +129,7 @@ void save_fpregs_to_fpstate(struct fpu *fpu) { if (likely(use_xsave())) { os_xsave(fpu->fpstate); - - /* - * AVX512 state is tracked here because its use is - * known to slow the max clock speed of the core. - */ - if (fpu->fpstate->regs.xsave.header.xfeatures & XFEATURE_MASK_AVX512) - fpu->avx512_timestamp = jiffies; + update_avx_timestamp(fpu); return; } -- 2.30.2