On 21/02/19 18:15, Sean Christopherson wrote:
This bug exists only in the 4.4.y backport; upstream, 4.9.y and 4.14.y all had the correct code from the get-go. And there is already a KVM unit test that *should* hit this, albeit somewhat indirectly. I'll verify the tests that touch the TPR actually run with x2APIC enabled.
eventinj from kvm-unit-tests should trigger it. There are other tests that touch the TPR, but they use cr8 so they don't show the bug.
Assuming the KVM unit test actually works, it's not a stretch for the bug to esacpe, e.g. if the tests weren't run on 4.4.y at all, or were only run on hardware with x2APIC.
Yeah, you should be able to see this with kvm_intel.enable_apicv=0 on newer processors. But I've never run the tests for 4.4.y.
Paolo