AMD General > -----Original Message----- > From: Jim Mattson <[email protected]> > Sent: Thursday, May 14, 2026 1:02 PM > To: Sean Christopherson <[email protected]>; Kaplan, David > <[email protected]> > Cc: [email protected]; [email protected]; [email protected]; > [email protected]; [email protected]; [email protected]; > [email protected]; [email protected]; [email protected]; linux- > [email protected]; [email protected]; [email protected] > Subject: Re: [PATCH v3 3/4] KVM: x86: Virtualize AMD CPUID faulting > > Caution: This message originated from an External Source. Use proper caution > when opening attachments, clicking links, or responding. > > > On Thu, May 14, 2026 at 9:35 AM Sean Christopherson > <[email protected]> wrote: > > > > On Thu, May 14, 2026, Jim Mattson wrote: > > > On Thu, May 14, 2026 at 9:20 AM Sean Christopherson > <[email protected]> wrote: > > > > Oooh, this is based on the generic CPL rules. I didn't think about it > > > > from > that > > > > perspective. So yeah, addressing that does make sense. What a pain. > > > > > > When I fix this in version 4, what's the correct footer for Sashiko > attribution: > > > > > > Assisted-by: Sashiko:gemini/gemini-3.1-pro-preview > > > > > > or > > > > > > Reported-by: Sashiko:gemini/gemini-3.1-pro-preview > > > > This, or even just: > > > > Reported-by: Sashiko > > > > is good enough for me. I don't expect random developers to know or care > what > > model was used, at least not when it comes to reporting bugs. If you use AI > to > > help write the code, then maybe I'd care? > > I had Jetski write an empirical test to see how the hardware behaves. > On the first userspace CPUID VM-exit, temporarily set #GP on userspace > CPUID per the appropriate vendor's mechanism, make sure that we > intercept #GP, and re-enter the guest without advancing RIP. Then, see > what the next VM-exit is. > > Surprise! > > kvm_intel: KVM: EMPIRICAL TEST RESULT: #GP took precedence over CPUID > VM-exit > kvm_amd: KVM: EMPIRICAL TEST RESULT (SVM): CPUID VM-exit took > precedence over #GP! > > LOL! > > David: Is this intentional or a bug?
This appears to be a bug, as most other instructions (e.g. INVPCID) that have CPL checks do the CPL checks before the VMEXIT checks. I'm following up on this internally... Thanks for bringing this to our attention --David Kaplan
