On 06-08-2025 00:35, Sean Christopherson wrote: > This is a prep series for the mediated PMU, and for Xin's series to add > support for the immediate forms of RDMSR and WRMSRNS (I'll post a v3 of > that series on top of this). > > The first half cleans up a variety of warts and flaws in the VM-Exit fastpath > handlers. The second half cleans up the PMU code related to "triggering" > instruction retired and branches retired events. The end goal of the two > halves (other than general cleanup) is to be able bail from the fastpath when > using the mediated PMU and the guest is counting instructions retired, with > minimal overhead, e.g. without having to acquire SRCU. > > Because the mediated PMU context switches PMU state _outside_ of the fastpath, > the mediated PMU won't be able to increment PMCs in the fastpath, and so won't > be able to skip emulated instructions in the fastpath if the vCPU is counting > instructions retired. > > The last patch to handle INVD in the fastpath is a bit dubious. It works just > fine, but it's dangerously close to "just because we can, doesn't mean we > should" territory. I added INVD to the fastpath before I realized that > MSR_IA32_TSC_DEADLINE could be handled in the fastpath irrespective of the > VMX preemption timer, i.e. on AMD CPUs. But being able to use INVD to test > the fastpath is still super convenient, as there are no side effects (unless > someone ran the test on bare metal :-D), no register constraints, and no > vCPU model requirements. So, I kept it, because I couldn't come up with a > good reason not to. > > Sean Christopherson (18): > KVM: SVM: Skip fastpath emulation on VM-Exit if next RIP isn't valid > KVM: x86: Add kvm_icr_to_lapic_irq() helper to allow for fastpath IPIs > KVM: x86: Only allow "fast" IPIs in fastpath WRMSR(X2APIC_ICR) handler > KVM: x86: Drop semi-arbitrary restrictions on IPI type in fastpath > KVM: x86: Unconditionally handle MSR_IA32_TSC_DEADLINE in fastpath > exits > KVM: x86: Acquire SRCU in WRMSR fastpath iff instruction needs to be > skipped > KVM: x86: Unconditionally grab data from EDX:EAX in WRMSR fastpath > KVM: x86: Fold WRMSR fastpath helpers into the main handler > KVM: x86/pmu: Move kvm_init_pmu_capability() to pmu.c > KVM: x86/pmu: Add wrappers for counting emulated instructions/branches > KVM: x86/pmu: Calculate set of to-be-emulated PMCs at time of WRMSRs > KVM: x86/pmu: Rename pmc_speculative_in_use() to > pmc_is_locally_enabled() > KVM: x86/pmu: Open code pmc_event_is_allowed() in its callers > KVM: x86/pmu: Drop redundant check on PMC being globally enabled for > emulation > KVM: x86/pmu: Drop redundant check on PMC being locally enabled for > emulation > KVM: x86/pmu: Rename check_pmu_event_filter() to > pmc_is_event_allowed() > KVM: x86: Push acquisition of SRCU in fastpath into > kvm_pmu_trigger_event() > KVM: x86: Add a fastpath handler for INVD > > arch/x86/include/asm/kvm_host.h | 3 + > arch/x86/kvm/lapic.c | 59 ++++++++---- > arch/x86/kvm/lapic.h | 3 +- > arch/x86/kvm/pmu.c | 155 +++++++++++++++++++++++++------- > arch/x86/kvm/pmu.h | 60 ++----------- > arch/x86/kvm/svm/svm.c | 14 ++- > arch/x86/kvm/vmx/nested.c | 2 +- > arch/x86/kvm/vmx/pmu_intel.c | 2 +- > arch/x86/kvm/vmx/vmx.c | 2 + > arch/x86/kvm/x86.c | 85 +++++------------- > arch/x86/kvm/x86.h | 1 + > 11 files changed, 218 insertions(+), 168 deletions(-) > > > base-commit: 196d9e72c4b0bd68b74a4ec7f52d248f37d0f030 No issues observed with KVM Unit Tests on recent AMD platforms (Milan, Genoa and Turin).
