| Message ID | 20240307011344.835640-1-seanjc@google.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | KVM: VMX: Disable LBRs if CPU doesn't have callstacks | expand |
On Wed, 06 Mar 2024 17:13:41 -0800, Sean Christopherson wrote: > Disable LBR virtualization if the CPU (or I guess perf) doesn't support > LBR callstacks, as KVM unconditionally creates the associated perf LBR > event with PERF_SAMPLE_BRANCH_CALL_STACK. That results in perf rejecting > the event, and cause LBR virtualization to silently fail. > > This was detected by running vmx_pmu_caps_test on older hardware. I didn't > tag it for stable because I can't imagine anyone is trying to use KVM's LBR > virtualization on pre-HSW. > > [...] Applied to kvm-x86 fixes, as I can't imagine anyone objecting to patch 2. [1/3] KVM: VMX: Snapshot LBR capabilities during module initialization https://github.com/kvm-x86/linux/commit/2a94a2761236 [2/3] perf/x86/intel: Expose existence of callback support to KVM https://github.com/kvm-x86/linux/commit/0c0241c12332 [3/3] KVM: VMX: Disable LBR virtualization if the CPU doesn't support LBR callstacks https://github.com/kvm-x86/linux/commit/0eb2416c8111 -- https://github.com/kvm-x86/linux/tree/next
Disable LBR virtualization if the CPU (or I guess perf) doesn't support LBR callstacks, as KVM unconditionally creates the associated perf LBR event with PERF_SAMPLE_BRANCH_CALL_STACK. That results in perf rejecting the event, and cause LBR virtualization to silently fail. This was detected by running vmx_pmu_caps_test on older hardware. I didn't tag it for stable because I can't imagine anyone is trying to use KVM's LBR virtualization on pre-HSW. Sean Christopherson (3): KVM: VMX: Snapshot LBR capabilities during module initialization perf/x86/intel: Expose existence of callback support to KVM KVM: VMX: Disable LBR virtualization if the CPU doesn't support LBR callstacks arch/x86/events/intel/lbr.c | 1 + arch/x86/include/asm/perf_event.h | 1 + arch/x86/kvm/vmx/pmu_intel.c | 2 +- arch/x86/kvm/vmx/vmx.c | 17 +++++++++++++---- arch/x86/kvm/vmx/vmx.h | 2 ++ 5 files changed, 18 insertions(+), 5 deletions(-) base-commit: 0c64952fec3ea01cb5b09f00134200f3e7ab40d5