linux-kernel - Re: [PATCH v4 09/25] KVM: VMX: nVMX: Support TSC scaling and PERF_GLOBAL

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Message-ID: <62ac29cb-3270-a810-bad1-3692da448016@redhat.com>
Date:   Fri, 29 Jul 2022 00:24:59 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     Vitaly Kuznetsov <vkuznets@...hat.com>, kvm@...r.kernel.org,
        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 v4 09/25] KVM: VMX: nVMX: Support TSC scaling and
 PERF_GLOBAL_CTRL with enlightened VMCS

On 7/29/22 00:13, Sean Christopherson wrote:
> The only flaw in this is if KVM gets handed a CPUID model that enumerates support
> for 2025 (or whenever the next update comes) but not 2022.  Hmm, though if Microsoft
> defines each new "version" as a full superset, then even that theoretical bug goes
> away.  I'm happy to be optimistic for once and give this a shot.  I definitely like
> that it makes it easier to see the deltas between versions.

Okay, I have queued the series but I still haven't gone through all the 
comments.  So this will _not_ be in the 5.21 pull request.

The first patch also needs a bit more thought to figure out the impact 
on userspace and whether we can consider syndbg niche enough to not care.

Paolo