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

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Date:   Wed, 6 Jul 2022 22:30:05 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Jim Mattson <jmattson@...gle.com>
Cc:     Vitaly Kuznetsov <vkuznets@...hat.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Anirudh Rayabharam <anrayabh@...ux.microsoft.com>,
        kvm@...r.kernel.org, Wanpeng Li <wanpengli@...cent.com>,
        Maxim Levitsky <mlevitsk@...hat.com>,
        linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 00/14] KVM: nVMX: Use vmcs_config for setting up nested
 VMX MSRs

On Wed, Jun 29, 2022, Jim Mattson wrote:
> On Wed, Jun 29, 2022 at 2:06 AM Vitaly Kuznetsov <vkuznets@...hat.com> 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.