Re: [RFC 7/7] KVM: VMX: Enable PKS for nested VM

[Chenyi Qiang]

On 8/14/2020 1:52 AM, Jim Mattson wrote:
> On Wed, Aug 12, 2020 at 9:54 PM Chenyi Qiang <chenyi.qiang@xxxxxxxxx> wrote:
> > On 8/11/2020 8:05 AM, Jim Mattson wrote:
> > > On Fri, Aug 7, 2020 at 1:47 AM Chenyi Qiang <chenyi.qiang@xxxxxxxxx> wrote:
> > > > PKS MSR passes through guest directly. Configure the MSR to match the
> > > > L0/L1 settings so that nested VM runs PKS properly.
> > > >
> > > > Signed-off-by: Chenyi Qiang <chenyi.qiang@xxxxxxxxx>
> > > > ---
>
> > > > +           (!vmx->nested.nested_run_pending ||
> > > > +            !(vmcs12->vm_entry_controls & VM_ENTRY_LOAD_IA32_PKRS)))
> > > > +               vmcs_write64(GUEST_IA32_PKRS, vmx->nested.vmcs01_guest_pkrs);
> > >
> > > This doesn't seem right to me. On the target of a live migration, with
> > > L2 active at the time the snapshot was taken (i.e.,
> > > vmx->nested.nested_run_pending=0), it looks like we're going to try to
> > > overwrite the current L2 PKRS value with L1's PKRS value (except that
> > > in this situation, vmx->nested.vmcs01_guest_pkrs should actually be
> > > 0). Am I missing something?
> >
> > We overwrite the L2 PKRS with L1's value when L2 doesn't support PKS.
> > Because the L1's VM_ENTRY_LOAD_IA32_PKRS is off, we need to migrate L1's
> > PKRS to L2.
>
> I'm thinking of the case where vmx->nested.nested_run_pending is
> false, and we are processing a KVM_SET_NESTED_STATE ioctl, yet
> VM_ENTRY_LOAD_IA32_PKRS *is* set in the vmcs12.

Oh, I miss this case. What I'm still confused here is that the 
restoration for GUEST_IA32_DEBUGCTL and GUEST_BNDCFGS have the same 
issue, right? or I miss something.