[tip: perf/core] perf/x86/intel: KVM: Handle cross-mapped PEBS PMCs entirely within KVM

[tip-bot2 for Sean Christopherson]

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

Commit-ID:     31f7cf337ce717666ce29fbd793f06435eb48408
Gitweb:        https://git.kernel.org/tip/31f7cf337ce717666ce29fbd793f06435eb48408
Author:        Sean Christopherson <seanjc@xxxxxxxxxx>
AuthorDate:    Mon, 21 Sep 2026 12:14:15 -07:00
Committer:     Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Fri, 25 Sep 2026 12:45:53 +02:00

perf/x86/intel: KVM: Handle cross-mapped PEBS PMCs entirely within KVM

Now that perf operates on a KVM-provided snapshot of PMU state, handled
cross-mapped PEBS counters entirely in KVM by clearing unusable counters
from the to-be-enabled mask instead of foisting the work on perf.

No functional change intended.

Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Reviewed-by: Dapeng Mi <dapeng1.mi@xxxxxxxxxxxxxxx>
Link: https://patch.msgid.link/20260921191418.950933-8-seanjc@xxxxxxxxxx
---
 arch/x86/events/intel/core.c      |  8 --------
 arch/x86/include/asm/perf_event.h |  1 -
 arch/x86/kvm/vmx/vmx.c            | 10 ++++++++--
 3 files changed, 8 insertions(+), 11 deletions(-)

diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
index 87274b3..1bc96b9 100644
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -5390,14 +5390,6 @@ static struct perf_guest_switch_msr *intel_guest_get_msrs(int *nr,
 			  cpuc->intel_ctrl_exclude_host_mask;
 
 	/*
-	 * Disable counters where the guest PMC is different than the host PMC
-	 * being used on behalf of the guest, as the PEBS record includes
-	 * PERF_GLOBAL_STATUS, i.e. the guest will see overflow status for the
-	 * wrong counter(s).
-	 */
-	guest_pebs_mask &= ~guest_pebs->cross_mapped_mask;
-
-	/*
 	 * FIXME: Allow guest and host usage of PEBS events to co-exist instead
 	 *        of disabling guest PEBS entirely if the host is using PEBS.
 	 *        What exactly goes wrong if guest and host are using PEBS is
diff --git a/arch/x86/include/asm/perf_event.h b/arch/x86/include/asm/perf_event.h
index 27f9c5b..5c92d43 100644
--- a/arch/x86/include/asm/perf_event.h
+++ b/arch/x86/include/asm/perf_event.h
@@ -823,7 +823,6 @@ struct x86_guest_pebs {
 	u64	enable;
 	u64	ds_area;
 	u64	data_cfg;
-	u64	cross_mapped_mask;
 };
 #if defined(CONFIG_PERF_EVENTS) && defined(CONFIG_CPU_SUP_INTEL)
 extern struct perf_guest_switch_msr *perf_guest_get_msrs(int *nr,
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index b097db2..8f7d062 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -7369,8 +7369,14 @@ static void atomic_switch_perf_msrs(struct vcpu_vmx *vmx)
 		.data_cfg = pmu->pebs_data_cfg,
 	};
 
-	if (pmu->pebs_enable & pmu->global_ctrl)
-		guest_pebs.cross_mapped_mask = intel_pmu_get_cross_mapped_mask(pmu);
+	/*
+	 * Disable counters where the guest PMC is different than the host PMC
+	 * being used on behalf of the guest, as the PEBS record includes
+	 * PERF_GLOBAL_STATUS, i.e. the guest will see overflow status for the
+	 * wrong counter(s).
+	 */
+	if (guest_pebs.enable & pmu->global_ctrl)
+		guest_pebs.enable &= ~intel_pmu_get_cross_mapped_mask(pmu);
 
 	/* Note, nr_msrs may be garbage if perf_guest_get_msrs() returns NULL. */
 	msrs = perf_guest_get_msrs(&nr_msrs, &guest_pebs);