linux-kernel - Re: [PATCH] KVM: x86: Disallow setting CPUID and/or feature MSRs if L2 is active

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Message-ID: <176823946368.1376238.573077114013944949.b4-ty@google.com>
Date: Mon, 12 Jan 2026 09:38:40 -0800
From: Sean Christopherson <seanjc@...gle.com>
To: Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Yosry Ahmed <yosry.ahmed@...ux.dev>, Kevin Cheng <chengkev@...gle.com>
Subject: Re: [PATCH] KVM: x86: Disallow setting CPUID and/or feature MSRs if
 L2 is active

On Tue, 30 Dec 2025 12:56:41 -0800, Sean Christopherson wrote:
> Extend KVM's restriction on CPUID and feature MSR changes to disallow
> updates while L2 is active in addition to rejecting updates after the vCPU
> has run at least once.  Like post-run vCPU model updates, attempting to
> react to model changes while L2 is active is practically infeasible, e.g.
> KVM would need to do _something_ in response to impossible situations where
> userspace has a removed a feature that was consumed as parted of nested
> VM-Enter.
> 
> [...]

Applied to kvm-x86 misc, thanks!

[1/1] KVM: x86: Disallow setting CPUID and/or feature MSRs if L2 is active
      https://github.com/kvm-x86/linux/commit/b47b93c15b12

--
https://github.com/kvm-x86/linux/tree/next