Re: [PATCH v2 1/6] KVM: SVM: Use maxphyaddr in emulator RAX check for VMRUN/VMLOAD/VMSAVE

[Sean Christopherson]

On Fri, Mar 06, 2026, Yosry Ahmed wrote:
> > > Right, but I am trying to have the #GP check for VMLOAD/VMSAVE behave
> > > consistently with vls=1, whether it's done by the hardware or the
> > > emulator.
> >
> > Consistency should not be an issue, since VLS cannot be enabled when
> > the MAXPHYADDRs differ. VLS doesn't work in that scenario.
> 
> Why? It's only broken if VMLOAD/VMSAVE is executed with a GPA that
> exceeds the guest's MAXPHYADDR, but not the host's, right? So only
> broken if the guest is misbehaving.
> 
> Taking a step back, I am not disagreeing that VLS should not be used
> with different MAXPHYADDRs, I am just saying it might be.

KVM straight up doesn't support that (see my other reply).

> All that being said, I am fine with using cpuid_maxphyaddr(vcpu)
> instead of kvm_host.maxphyaddr. Will wait for Sean's feedback to
> figure out if a new version is needed.

LOL, Jim and I are of one mind when it comes to guest.MAXPHYADDR.