Re: [PATCH v1 3/5] KVM: x86: nVMX: VMCS12 field's read/write respects field existence bitmap

[Sean Christopherson <seanjc@google.com>]

On Wed, Nov 10, 2021, Yu Zhang wrote:
> On Tue, Nov 09, 2021 at 10:33:43PM +0000, Sean Christopherson wrote:
> > On Wed, Nov 03, 2021, Robert Hoo wrote:
> > > On Fri, 2021-10-29 at 12:53 -0700, Jim Mattson wrote:
> > > > On Fri, Oct 8, 2021 at 5:05 PM Robert Hoo <robert.hu@linux.intel.com>
> > > > wrote:
> > > > > 
> > > > > On Fri, 2021-10-08 at 16:49 -0700, Jim Mattson wrote:
> > > > > > We have some internal patches for virtualizing VMCS shadowing
> > > > > > which
> > > > > > may break if there is a guest VMCS field with index greater than
> > > > > > VMX_VMCS_ENUM.MAX_INDEX. I plan to upstream them soon.
> > > > > 
> > > > > OK, thanks for letting us know.:-)
> > > > 
> > > > After careful consideration, we're actually going to drop these
> > > > patches rather than sending them upstream.
> > > 
> > > OK.
> > > 
> > > Hi, Paolo, Sean and Jim,
> > > 
> > > Do you think our this series patch are still needed or can be dropped
> > > as well?
> > 
> > IMO we should drop this series and take our own erratum.
> > 
> 
> Thanks, Sean.
> 
> Do we need a patch in kvm-unit-test to depricate the check against
> the max index from MSR_IA32_VMX_VMCS_ENUM?

Hmm, yes, unless there's an easy way to tell QEMU to not override the VMX MSRs.
I don't see any point in fighting too hard with QEMU.