This is a note to let you know that I've just added the patch titled
powerpc/perf: Fix disabling BHRB and instruction sampling
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
powerpc-perf-fix-disabling-bhrb-and-instruction-sampling.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From ea142e590aec55ba40c5affb4d49e68c713c63dc Mon Sep 17 00:00:00 2001
From: Nicholas Piggin <npiggin@xxxxxxxxx>
Date: Thu, 19 Oct 2023 01:34:23 +1000
Subject: powerpc/perf: Fix disabling BHRB and instruction sampling
From: Nicholas Piggin <npiggin@xxxxxxxxx>
commit ea142e590aec55ba40c5affb4d49e68c713c63dc upstream.
When the PMU is disabled, MMCRA is not updated to disable BHRB and
instruction sampling. This can lead to those features remaining enabled,
which can slow down a real or emulated CPU.
Fixes: 1cade527f6e9 ("powerpc/perf: BHRB control to disable BHRB logic when not used")
Cc: stable@xxxxxxxxxxxxxxx # v5.9+
Signed-off-by: Nicholas Piggin <npiggin@xxxxxxxxx>
Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Link: https://msgid.link/20231018153423.298373-1-npiggin@xxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/powerpc/perf/core-book3s.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
--- a/arch/powerpc/perf/core-book3s.c
+++ b/arch/powerpc/perf/core-book3s.c
@@ -1342,8 +1342,7 @@ static void power_pmu_disable(struct pmu
/*
* Disable instruction sampling if it was enabled
*/
- if (cpuhw->mmcr.mmcra & MMCRA_SAMPLE_ENABLE)
- val &= ~MMCRA_SAMPLE_ENABLE;
+ val &= ~MMCRA_SAMPLE_ENABLE;
/* Disable BHRB via mmcra (BHRBRD) for p10 */
if (ppmu->flags & PPMU_ARCH_31)
@@ -1354,7 +1353,7 @@ static void power_pmu_disable(struct pmu
* instruction sampling or BHRB.
*/
if (val != mmcra) {
- mtspr(SPRN_MMCRA, mmcra);
+ mtspr(SPRN_MMCRA, val);
mb();
isync();
}
Patches currently in stable-queue which might be from npiggin@xxxxxxxxx are
queue-5.15/powerpc-perf-fix-disabling-bhrb-and-instruction-sampling.patch
