Jon Kohler <jon@xxxxxxxxxxx> writes: >> On May 4, 2022, at 5:47 PM, Sean Christopherson <seanjc@xxxxxxxxxx> wrote: >> ... > > The net problem here is really that the stat is likely incorrect; however, > one other oddity I didn’t quite understand after looking into this is that > the call site for all of this is in record_steal_time(), which is only called > from vcpu_enter_guest(), and that is called *after* > kvm_service_local_tlb_flush_requests(), which also calls > kvm_vcpu_flush_tlb_guest() if request == KVM_REQ_TLB_FLUSH_GUEST > > That request may be there set from a few different places. > > I don’t have any proof of this, but it seems to me like we might have a > situation where we double flush? > > Put another way, I wonder if there is any sense behind maybe hoisting > if (kvm_check_request(KVM_REQ_STEAL_UPDATE, vcpu)) up before > Other tlb flushes, and have it clear the FLUSH_GUEST if it was set? Indeed, if we move KVM_REQ_STEAL_UPDATE check/record_steal_time() call in vcpu_enter_guest() before kvm_service_local_tlb_flush_requests(), we can probably get aways with kvm_make_request(KVM_REQ_TLB_FLUSH_GUEST, vcpu) in record_steal_time() which would help to avoid double flushing. -- Vitaly
