The following commit has been merged into the x86/fpu branch of tip:
Commit-ID: 0fe4ff885f8a50082d9dc241b657472894caba16
Gitweb: https://git.kernel.org/tip/0fe4ff885f8a50082d9dc241b657472894caba16
Author: Noah Goldstein <goldstein.w.n@xxxxxxxxx>
AuthorDate: Tue, 16 Nov 2021 17:14:21 +01:00
Committer: Borislav Petkov <bp@xxxxxxx>
CommitterDate: Tue, 16 Nov 2021 17:19:41 +01:00
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 <goldstein.w.n@xxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Link: https://lore.kernel.org/r/20210920053951.4093668-1-goldstein.w.n@xxxxxxxxx
---
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 8ea306b..dd3777a 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -99,6 +99,19 @@ 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;
}
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