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Merge tag 'x86_fpu_for_v5.17_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

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Pull x86 fpu update from Borislav Petkov:
 "A single x86/fpu update for 5.17:

   - Exclude AVX opmask registers use from AVX512 state tracking as they
     don't contribute to frequency throttling"

* tag 'x86_fpu_for_v5.17_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/fpu: Correct AVX512 state tracking
This commit is contained in:
Linus Torvalds
2022-01-10 09:05:26 -08:00
parent 8cc1e20765 0fe4ff885f
commit 191cf7fab9
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;
}