[Patch v6 01/22] perf/x86/intel: Restrict PEBS_ENABLE writes to PEBS-capable counters

[Dapeng Mi <dapeng1.mi@linux.intel.com>]

Before the introduction of extended PEBS, PEBS supported only
general-purpose (GP) counters. In a virtual machine (VM) environment,
the PEBS_BASELINE bit in PERF_CAPABILITIES may not be set, but the PEBS
format could be indicated as 4 or higher. In such cases, PEBS events
might be scheduled to fixed counters, and writing the corresponding bits
into the PEBS_ENABLE MSR could cause a #GP fault.

To prevent writing unsupported bits into the PEBS_ENABLE MSR, ensure
cpuc->pebs_enabled aligns with x86_pmu.pebs_capable and restrict the
writes to only PEBS-capable counter bits.

Signed-off-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
---

V6: new patch.

 arch/x86/events/intel/core.c |  6 ++++--
 arch/x86/events/intel/ds.c   | 11 +++++++----
 2 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
index f3ae1f8ee3cd..546ebc7e1624 100644
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -3554,8 +3554,10 @@ static int handle_pmi_common(struct pt_regs *regs, u64 status)
 		 * cpuc->enabled has been forced to 0 in PMI.
 		 * Update the MSR if pebs_enabled is changed.
 		 */
-		if (pebs_enabled != cpuc->pebs_enabled)
-			wrmsrq(MSR_IA32_PEBS_ENABLE, cpuc->pebs_enabled);
+		if (pebs_enabled != cpuc->pebs_enabled) {
+			wrmsrq(MSR_IA32_PEBS_ENABLE,
+			       cpuc->pebs_enabled & x86_pmu.pebs_capable);
+		}
 
 		/*
 		 * Above PEBS handler (PEBS counters snapshotting) has updated fixed
diff --git a/arch/x86/events/intel/ds.c b/arch/x86/events/intel/ds.c
index 5027afc97b65..57805c6ba0c3 100644
--- a/arch/x86/events/intel/ds.c
+++ b/arch/x86/events/intel/ds.c
@@ -1963,6 +1963,7 @@ void intel_pmu_pebs_disable(struct perf_event *event)
 {
 	struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
 	struct hw_perf_event *hwc = &event->hw;
+	u64 pebs_enabled;
 
 	__intel_pmu_pebs_disable(event);
 
@@ -1974,16 +1975,18 @@ void intel_pmu_pebs_disable(struct perf_event *event)
 
 	intel_pmu_pebs_via_pt_disable(event);
 
-	if (cpuc->enabled)
-		wrmsrq(MSR_IA32_PEBS_ENABLE, cpuc->pebs_enabled);
+	pebs_enabled = cpuc->pebs_enabled & x86_pmu.pebs_capable;
+	if (pebs_enabled)
+		wrmsrq(MSR_IA32_PEBS_ENABLE, pebs_enabled);
 }
 
 void intel_pmu_pebs_enable_all(void)
 {
 	struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
+	u64 pebs_enabled = cpuc->pebs_enabled & x86_pmu.pebs_capable;
 
-	if (cpuc->pebs_enabled)
-		wrmsrq(MSR_IA32_PEBS_ENABLE, cpuc->pebs_enabled);
+	if (pebs_enabled)
+		wrmsrq(MSR_IA32_PEBS_ENABLE, pebs_enabled);
 }
 
 void intel_pmu_pebs_disable_all(void)
-- 
2.34.1