Bug fixes and cleanups related to KVM's handling of PERF_CAPABILITIES. Bug #1 - Refresh KVM's vPMU after userspace writes PERF_CAPABILITIES, and then leverage that fix to avoiding checking guest_cpuid_has(X86_FEATURE_PDCM) during VM-Enter, which is slow enough that it shows up in perf traces[*]. Bug #2 - Don't advertise PMU_CAP_LBR_FMT to userspace if perf has disabled LBRs, e.g. because probing one or more LBR MSRs during setup hit a #GP. The non-KVM patches remove unnecessary stubs and unreachable error paths, which allows for a cleaner fix for bug #2. [*] https://gist.github.com/avagin/f50a6d569440c9ae382281448c187f4e v2: - Add patches to fix bug #2. [Like] - Add a patch to clean up the capability check. - Tweak the changelog for the PMU refresh bug fix to call out that KVM should disallow changing feature MSRs after KVM_RUN. [Like] v1: https://lore.kernel.org/all/20220727233424.2968356-1-seanjc@xxxxxxxxxx Sean Christopherson (7): KVM: x86: Refresh PMU after writes to MSR_IA32_PERF_CAPABILITIES perf/x86/core: Remove unnecessary stubs provided for KVM-only helpers perf/x86/core: Drop the unnecessary return value from x86_perf_get_lbr() KVM: VMX: Advertise PMU LBRs if and only if perf supports LBRs KVM: VMX: Use proper type-safe functions for vCPU => LBRs helpers KVM: VMX: Adjust number of LBR records for PERF_CAPABILITIES at refresh KVM: VMX: Simplify capability check when handling PERF_CAPABILITIES write arch/x86/events/intel/lbr.c | 6 +--- arch/x86/include/asm/perf_event.h | 55 ++++++++----------------------- arch/x86/kvm/vmx/capabilities.h | 5 ++- arch/x86/kvm/vmx/pmu_intel.c | 12 ++----- arch/x86/kvm/vmx/vmx.c | 6 ++-- arch/x86/kvm/vmx/vmx.h | 53 +++++++++++++++++------------ arch/x86/kvm/x86.c | 4 +-- 7 files changed, 58 insertions(+), 83 deletions(-) base-commit: 93472b79715378a2386598d6632c654a2223267b -- 2.37.1.559.g78731f0fdb-goog
