linux-kernel - [tip: perf/urgent] perf/x86/amd/core: Avoid register reset when CPU is dead

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Message-ID: <171032535648.398.6298108731990613596.tip-bot2@tip-bot2>
Date: Wed, 13 Mar 2024 10:22:36 -0000
From: "tip-bot2 for Sandipan Das" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Mario Limonciello <mario.limonciello@....com>,
 Sandipan Das <sandipan.das@....com>, Ingo Molnar <mingo@...nel.org>,
 Peter Zijlstra <peterz@...radead.org>, x86@...nel.org,
 linux-kernel@...r.kernel.org
Subject:
 [tip: perf/urgent] perf/x86/amd/core: Avoid register reset when CPU is dead

The following commit has been merged into the perf/urgent branch of tip:

Commit-ID:     ad8c91282c95f801c37812d59d2d9eba6899b384
Gitweb:        https://git.kernel.org/tip/ad8c91282c95f801c37812d59d2d9eba6899b384
Author:        Sandipan Das <sandipan.das@....com>
AuthorDate:    Mon, 29 Jan 2024 16:36:26 +05:30
Committer:     Ingo Molnar <mingo@...nel.org>
CommitterDate: Wed, 13 Mar 2024 11:01:30 +01:00

perf/x86/amd/core: Avoid register reset when CPU is dead

When bringing a CPU online, some of the PMC and LBR related registers
are reset. The same is done when a CPU is taken offline although that
is unnecessary. This currently happens in the "cpu_dead" callback which
is also incorrect as the callback runs on a control CPU instead of the
one that is being taken offline. This also affects hibernation and
suspend to RAM on some platforms as reported in the link below.

Fixes: 21d59e3e2c40 ("perf/x86/amd/core: Detect PerfMonV2 support")
Reported-by: Mario Limonciello <mario.limonciello@....com>
Signed-off-by: Sandipan Das <sandipan.das@....com>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Link: https://lore.kernel.org/r/550a026764342cf7e5812680e3e2b91fe662b5ac.1706526029.git.sandipan.das@amd.com
---
 arch/x86/events/amd/core.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/arch/x86/events/amd/core.c b/arch/x86/events/amd/core.c
index 69a3b02..aec16e5 100644
--- a/arch/x86/events/amd/core.c
+++ b/arch/x86/events/amd/core.c
@@ -604,7 +604,6 @@ static void amd_pmu_cpu_dead(int cpu)
 
 	kfree(cpuhw->lbr_sel);
 	cpuhw->lbr_sel = NULL;
-	amd_pmu_cpu_reset(cpu);
 
 	if (!x86_pmu.amd_nb_constraints)
 		return;