On Mon, Aug 18, 2025 at 08:25:34AM -0700, Sean Christopherson wrote: > > OK, so *IF* doing the VM-exit during PMI is sound, this is something > > that needs a comment somewhere. > > I'm a bit lost here. Are you essentially asking if it's ok to take a VM-Exit > while the guest is handling a PMI? If so, that _has_ to work, because there are > myriad things that can/will trigger a VM-Exit at any point while the guest is > active. Yes, that's what I'm asking. Why is this VM-exit during PMI nonsense not subject to the same failures that mandates the mid/late PMI ACK. And yes, I realize this needs to work. But so far I'm not sure I understand why that is a safe thing to do. Like I wrote, I suspect writing all the PMU MSRs serializes things sufficiently, but if that is the case, that needs to be explicitly mentioned. Because that also doesn't explain why we needs mid-ack instead of late-ack on ADL e-cores for instance. Could it perhaps be that we don't let the guests do PEBS because DS doesn't virtualize? And thus we don't have the malformed PEBS record?
