Re: [PATCH V4 0/4] Align SVM with APM defined behaviors

[Sean Christopherson <seanjc@google.com>]

On Mon, Mar 02, 2026, Sean Christopherson wrote:
> On Mon, Mar 02, 2026, Sean Christopherson wrote:
> > On Mon, Mar 02, 2026, Yosry Ahmed wrote:
> > > Also taking a step back, I am not really sure what's the right thing
> > > to do for Intel-compatible guests here. It also seems like even if we
> > > set the intercept, svm_set_gif() will clear the STGI intercept, even
> > > on Intel-compatible guests.
> > > 
> > > Maybe we should leave that can of worms alone, go back to removing
> > > initializing the CLGI/STGI intercepts in init_vmcb(), and in
> > > svm_recalc_instruction_intercepts() set/clear these intercepts based
> > > on EFER.SVME alone, irrespective of Intel-compatibility?
> > 
> > Ya, guest_cpuid_is_intel_compatible() should only be applied to VMLOAD/VMSAVE.
> > KVM intercepts VMLOAD/VMSAVE to fixup SYSENTER MSRs, not to inject #UD.  I.e. KVM
> > is handling (the absoutely absurd) case that FMS reports an Intel CPU, but the
> > guest enables and uses SVM.
> > 
> > 	/*
> > 	 * Intercept VMLOAD if the vCPU model is Intel in order to emulate that
> > 	 * VMLOAD drops bits 63:32 of SYSENTER (ignoring the fact that exposing
> > 	 * SVM on Intel is bonkers and extremely unlikely to work).
> > 	 */
> > 	if (guest_cpuid_is_intel_compatible(vcpu))
> > 		guest_cpu_cap_clear(vcpu, X86_FEATURE_V_VMSAVE_VMLOAD);
> > 
> > Sorry for not catching this in previous versions.
> 
> Because I got all kinds of confused trying to recall what was different between
> v3 and v4, I went ahead and spliced them together.
> 
> Does the below look right?  If so, I'll formally post just patches 1 and 3 as v5.
> I'll take 2 and 4 directly from here; I want to switch the ordering anyways so
> that the vgif movement immediately precedes the Recalc "instructions" patch.

Actually, I partially take that back.  I'm going to send a separate v5 for patch
4, as there are additional cleanups that can be done related to Hyper-V stubs.

P.S. This is a good example of why bundling unrelated patches into series is
discouraged.