Re: [PATCH 00/14] KVM: nVMX: Use vmcs_config for setting up nested VMX MSRs

[Sean Christopherson]

On Wed, Jun 29, 2022, Jim Mattson wrote:
> On Wed, Jun 29, 2022 at 2:06 AM Vitaly Kuznetsov <vkuznets@xxxxxxxxxx> wrote:
> 
> > For PERF_GLOBAL_CTRL errata:
> > - We can move the filtering to vmx_vmexit_ctrl()/vmx_vmentry_ctrl()
> > preserving the status quo: KVM doesn't use the feature but it is exposed
> > to L1 hypervisor (and L1 hypervisor presumably has the same check and
> > doesn't use the feature. FWIW, the workaround was added in 2011 and the
> > erratas it references appeared in 2010, this means that the affected
> > CPUs are quite old, modern proprietary hypervisors won't likely boot
> > there).
> Sadly, Nehalem and Westmere are well-supported by KVM today, and we
> will probably still continue to support them for at least another
> decade. They both have EPT, unrestricted guest, and other VT-x2
> features that KVM still considers optional.

Nehalem doesn't have unrestricted guest.  Nehalem is the only generation with EPT
but not unrestricted guest.