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x86/fpu: Correct AVX512 state tracking

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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 <goldstein.w.n@gmail.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20210920053951.4093668-1-goldstein.w.n@gmail.com
This commit is contained in:
Noah Goldstein 2021-11-16 17:14:21 +01:00 committed by Borislav Petkov
parent fa55b7dcdc
commit 0fe4ff885f
1 changed files with 14 additions and 7 deletions
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21
arch/x86/kernel/fpu/core.c
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@ -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;
}