[PATCH v4 0/6] KVM: x86/pmu: Add support for AMD Host-Only/Guest-Only bits

Yosry Ahmed
2026-03-26T03:12:31Z

v4 of Jim's series adding support for AMD's Host-Only and Guest-Only
performance counter eventsel bits in KVM's mediated PMU passthrough
implementation.

These bits allow an nSVM-enabled guest to configure performance counters
that count only during L1 execution (Host-Only) or only during L2 execution
(Guest-Only).

KVM updates the hardware event selector ENABLE bit at the following state
transitions to ensure counters only count in the appropriate mode:

- EFER.SVME changes: Enable/disable Guest-Only counters
- Nested VMRUN: Disable Host-Only, enable Guest-Only counters
- Nested VMEXIT: Enable Host-Only, disable Guest-Only counters

v3 -> v4:
- Dropped amd_pmu_set_eventsel_hw(), moved handling of
Host-Only/Guest-Only bits to PMU counter reprogramming and funnelled
all processing through KVM_REQ_PMU [Sean].
- For this to work, added a per-vendor callback for reprogramming PMU
counters.
- Sorta restored the bitmask from v1, except now it's a single bitmask
tracking all counters that need to be reprogrammed on nested
transitions. The bitmask is used to avoid unnecessary KVM_REQ_PMU
requests and only reprogram counters as needed [Jim].
- This is also needed to avoid directling calling vendor code from
{enter/leave}_guest_mode() as requested by Sean.
- Added prep patches moving enable_pmu/enable_mediated_pmu and
guest_mode helpers to facilitate following changes without circular
dependencies and to avoid including new headers from leaf headers.

v3: https://lore.kernel.org/kvm/20260207012339.2646196-1-jmattson@google.com/

Jim Mattson (2):
KVM: x86/pmu: Allow Host-Only/Guest-Only bits with nSVM and mediated
PMU
KVM: selftests: Add svm_pmu_host_guest_test for Host-Only/Guest-Only
bits

Yosry Ahmed (4):
KVM: x86: Move enable_pmu/enable_mediated_pmu to pmu.h and pmu.c
KVM: x86: Move guest_mode helpers to x86.h
KVM: x86/pmu: Disable counters based on Host-Only/Guest-Only bits in
SVM
KVM: x86/pmu: Re-evaluate Host-Only/Guest-Only on nested SVM
transitions

arch/x86/include/asm/kvm-x86-pmu-ops.h | 1 +
arch/x86/include/asm/kvm_host.h | 6 +
arch/x86/include/asm/perf_event.h | 2 +
arch/x86/kvm/kvm_cache_regs.h | 23 --
arch/x86/kvm/pmu.c | 12 ++
arch/x86/kvm/pmu.h | 17 ++
arch/x86/kvm/svm/pmu.c | 44 ++++
arch/x86/kvm/svm/svm.c | 1 +
arch/x86/kvm/x86.c | 9 -
arch/x86/kvm/x86.h | 31 ++-
tools/testing/selftests/kvm/Makefile.kvm | 1 +
tools/testing/selftests/kvm/include/x86/pmu.h | 6 +
.../selftests/kvm/include/x86/processor.h | 2 +
.../kvm/x86/svm_pmu_host_guest_test.c | 199 ++++++++++++++++++
14 files changed, 319 insertions(+), 35 deletions(-)
create mode 100644 tools/testing/selftests/kvm/x86/svm_pmu_host_guest_test.c

base-commit: 3d6cdcc8883b5726513d245eef0e91cabfc397f7
--
2.53.0.1018.g2bb0e51243-goog