On Mon, Sep 11, 2023, Mingwei Zhang wrote: > On Mon, Sep 11, 2023 at 8:01 AM Sean Christopherson <seanjc@xxxxxxxxxx> wrote: > > > > On Mon, Sep 11, 2023, Mingwei Zhang wrote: > > > Use atomic bit operations for pmu->global_status because it may suffer from > > > race conditions between emulated overflow in KVM vPMU and PEBS overflow in > > > host PMI handler. > > > > Only if the host PMI occurs on a different pCPU, and if that can happen don't we > > have a much larger problem? > > Why on different pCPU? For vPMU, I think there is always contention > between the vCPU thread and the host PMI handler running on the same > pCPU, no? A non-atomic instruction can't be interrupted by an NMI, or any other event, so I don't see how switching to atomic operations fixes anything unless the NMI comes in on a different pCPU.
