linux-kernel - [PATCH] perf/x86/amd/core: Fix reloading events for SVM

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Date:   Wed, 18 May 2022 14:13:27 +0530
From:   Sandipan Das <sandipan.das@....com>
To:     <linux-kernel@...r.kernel.org>, <linux-perf-users@...r.kernel.org>,
        <x86@...nel.org>
CC:     <peterz@...radead.org>, <bp@...en8.de>, <acme@...nel.org>,
        <namhyung@...nel.org>, <jolsa@...nel.org>, <tglx@...utronix.de>,
        <mingo@...hat.com>, <pbonzini@...hat.com>, <jmattson@...gle.com>,
        <like.xu.linux@...il.com>, <eranian@...gle.com>, <jroedel@...e.de>,
        <ananth.narayan@....com>, <ravi.bangoria@....com>,
        <santosh.shukla@....com>, <sandipan.das@....com>
Subject: [PATCH] perf/x86/amd/core: Fix reloading events for SVM

Commit 1018faa6cf23 ("perf/x86/kvm: Fix Host-Only/Guest-Only
counting with SVM disabled") addresses an issue in which the
Host-Only bit in the counter control registers needs to be
masked off when SVM is not enabled.

The events need to be reloaded whenever SVM is enabled or
disabled for a CPU and this requires the PERF_CTL registers
to be reprogrammed using {enable,disable}_all(). However,
PerfMonV2 variants of these functions do not reprogram the
PERF_CTL registers. Hence, the legacy enable_all() function
should also be called.

Fixes: 9622e67e3980 ("perf/x86/amd/core: Add PerfMonV2 counter control")
Reported-by: Like Xu <likexu@...cent.com>
Signed-off-by: Sandipan Das <sandipan.das@....com>
---
 arch/x86/events/amd/core.c | 24 ++++++++++++++++++++----
 1 file changed, 20 insertions(+), 4 deletions(-)

diff --git a/arch/x86/events/amd/core.c b/arch/x86/events/amd/core.c
index 359d575c27e2..37b175870ee8 100644
--- a/arch/x86/events/amd/core.c
+++ b/arch/x86/events/amd/core.c
@@ -1467,6 +1467,24 @@ __init int amd_pmu_init(void)
 	return 0;
 }
 
+static inline void amd_pmu_reload_virt(void)
+{
+	if (x86_pmu.version >= 2) {
+		/*
+		 * Clear global enable bits, reprogram the PERF_CTL
+		 * registers with updated perf_ctr_virt_mask and then
+		 * set global enable bits once again
+		 */
+		amd_pmu_v2_disable_all();
+		amd_pmu_enable_all(0);
+		amd_pmu_v2_enable_all(0);
+		return;
+	}
+
+	amd_pmu_disable_all();
+	amd_pmu_enable_all(0);
+}
+
 void amd_pmu_enable_virt(void)
 {
 	struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
@@ -1474,8 +1492,7 @@ void amd_pmu_enable_virt(void)
 	cpuc->perf_ctr_virt_mask = 0;
 
 	/* Reload all events */
-	amd_pmu_disable_all();
-	x86_pmu_enable_all(0);
+	amd_pmu_reload_virt();
 }
 EXPORT_SYMBOL_GPL(amd_pmu_enable_virt);
 
@@ -1492,7 +1509,6 @@ void amd_pmu_disable_virt(void)
 	cpuc->perf_ctr_virt_mask = AMD64_EVENTSEL_HOSTONLY;
 
 	/* Reload all events */
-	amd_pmu_disable_all();
-	x86_pmu_enable_all(0);
+	amd_pmu_reload_virt();
 }
 EXPORT_SYMBOL_GPL(amd_pmu_disable_virt);
-- 
2.34.1