linux-kernel - Re: [PATCH v2 08/28] KVM: VMX: Support TSC scaling with enlightened VMCS

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Date:   Thu, 07 Jul 2022 12:01:44 +0200
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>
Cc:     Anirudh Rayabharam <anrayabh@...ux.microsoft.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Maxim Levitsky <mlevitsk@...hat.com>,
        linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 08/28] KVM: VMX: Support TSC scaling with enlightened
 VMCS

Vitaly Kuznetsov <vkuznets@...hat.com> writes:

...

>
> While on it, update the comment why VM_EXIT_LOAD_IA32_PERF_GLOBAL_CTRL/
> VM_ENTRY_LOAD_IA32_PERF_GLOBAL_CTRL are kept filtered out

...

> + *	While GUEST_IA32_PERF_GLOBAL_CTRL and HOST_IA32_PERF_GLOBAL_CTRL
> + *	are present in eVMCSv1, Windows 11 still has issues booting when
> + *	VM_EXIT_LOAD_IA32_PERF_GLOBAL_CTRL/VM_ENTRY_LOAD_IA32_PERF_GLOBAL_CTRL
> + *	are exposed to it, keep them filtered out.

Finally, I got a piece of information from Microsoft on what's going on
and it solves a lot of our problems. They did introduce a new PV feature
bit indicating support for these new fields in eVMCSv1 and Win11 checks
for its presence. This means that we do not need to play the 'eVMCS
revisions' trick as CPUID information from VMM is enough.

-- 
Vitaly