Sean Christopherson f1c5651fda KVM: x86/pmu: Force reprogramming of all counters on PMU filter change ... Force vCPUs to reprogram all counters on a PMU filter change to provide a sane ABI for userspace. Use the existing KVM_REQ_PMU to do the programming, and take advantage of the fact that the reprogram_pmi bitmap fits in a u64 to set all bits in a single atomic update. Note, setting the bitmap and making the request needs to be done _after_ the SRCU synchronization to ensure that vCPUs will reprogram using the new filter. KVM's current "lazy" approach is confusing and non-deterministic. It's confusing because, from a developer perspective, the code is buggy as it makes zero sense to let userspace modify the filter but then not actually enforce the new filter. The lazy approach is non-deterministic because KVM enforces the filter whenever a counter is reprogrammed, not just on guest WRMSRs, i.e. a guest might gain/lose access to an event at random times depending on what is going on in the host. Note, the resulting behavior is still non-determinstic while the filter is in flux. If userspace wants to guarantee deterministic behavior, all vCPUs should be paused during the filter update. Jim Mattson <jmattson@google.com> Fixes: 66bb8a065f ("KVM: x86: PMU Event Filter") Cc: Aaron Lewis <aaronlewis@google.com> Signed-off-by: Sean Christopherson <seanjc@google.com> Message-Id: <20220923001355.3741194-2-seanjc@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>		2022-11-09 12:31:35 -05:00
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asm	KVM: x86/pmu: Force reprogramming of all counters on PMU filter change	2022-11-09 12:31:35 -05:00
uapi/asm	KVM: x86: Add a VALID_MASK for the flags in kvm_msr_filter_range	2022-11-09 12:31:30 -05:00