On Wed, Dec 13, 2023 at 2:25 PM Maxim Levitsky <mlevitsk@xxxxxxxxxx> wrote: > > On Tue, 2023-12-12 at 07:28 -0800, Sean Christopherson wrote: > > On Sun, Dec 10, 2023, Jim Mattson wrote: > > > On Thu, Dec 7, 2023 at 8:21 AM Sean Christopherson <seanjc@xxxxxxxxxx> wrote: > > > > Doh. We got the less obvious cases and missed the obvious one. > > > > > > > > Ugh, and we also missed a related mess in kvm_guest_apic_has_interrupt(). That > > > > thing should really be folded into vmx_has_nested_events(). > > > > > > > > Good gravy. And vmx_interrupt_blocked() does the wrong thing because that > > > > specifically checks if L1 interrupts are blocked. > > > > > > > > Compile tested only, and definitely needs to be chunked into multiple patches, > > > > but I think something like this mess? > > > > > > The proposed patch does not fix the problem. In fact, it messes things > > > up so much that I don't get any test results back. > > > > Drat. > > > > > Google has an internal K-U-T test that demonstrates the problem. I > > > will post it soon. > > > > Received, I'll dig in soonish, though "soonish" might unfortunately might mean > > 2024. > > > > Hi, > > So this is what I think: > > > KVM does have kvm_guest_apic_has_interrupt() for this exact purpose, > to check if nested APICv has a pending interrupt before halting. > > > However the problem is bigger - with APICv we have in essence 2 pending interrupt > bitmaps - the PIR and the IRR, and to know if the guest has a pending interrupt > one has in theory to copy PIR to IRR, then see if the max is larger then the current PPR. > > Since we don't want to write to guest memory, and the IRR here resides in the guest memory, > I guess we have to do a 'dry-run' version of 'vmx_complete_nested_posted_interrupt' and call > it from kvm_guest_apic_has_interrupt(). > > What do you think? I can prepare a patch for this. > > Can you share a reproducer or write a new one that can be shared? See https://lore.kernel.org/kvm/20231211185552.3856862-1-jmattson@xxxxxxxxxx/. > Best regards, > Maxim Levitsky >
