linux-kernel - [PATCH 6.6 549/638] perf/x86/amd/core: Avoid register reset when CPU is dead

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Message-ID: <20240324230116.1348576-550-sashal@kernel.org>
Date: Sun, 24 Mar 2024 18:59:46 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Sandipan Das <sandipan.das@....com>,
	Mario Limonciello <mario.limonciello@....com>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Sasha Levin <sashal@...nel.org>
Subject: [PATCH 6.6 549/638] perf/x86/amd/core: Avoid register reset when CPU is dead

From: Sandipan Das <sandipan.das@....com>

[ Upstream commit ad8c91282c95f801c37812d59d2d9eba6899b384 ]

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
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 e24976593a298..5365d6acbf090 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;
-- 
2.43.0