linux-kernel - Re: [PATCH] KVM: nVMX: Honor userspace MSR filter lists for nested VM-Enter/VM-Exit

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Message-ID: <172443876585.4128342.15040275219129929508.b4-ty@google.com>
Date: Fri, 23 Aug 2024 16:48:07 -0700
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, 
	Hou Wenlong <houwenlong.hwl@...group.com>, Jim Mattson <jmattson@...gle.com>
Subject: Re: [PATCH] KVM: nVMX: Honor userspace MSR filter lists for nested VM-Enter/VM-Exit

On Mon, 22 Jul 2024 16:59:22 -0700, Sean Christopherson wrote:
> Synthesize a consistency check VM-Exit (VM-Enter) or VM-Abort (VM-Exit) if
> L1 attempts to load/store an MSR via the VMCS MSR lists that userspace has
> disallowed access to via an MSR filter.  Intel already disallows including
> a handful of "special" MSRs in the VMCS lists, so denying access isn't
> completely without precedent.
> 
> More importantly, the behavior is well-defined _and_ can be communicated
> the end user, e.g. to the customer that owns a VM running as L1 on top of
> KVM.  On the other hand, ignoring userspace MSR filters is all but
> guaranteed to result in unexpected behavior as the access will hit KVM's
> internal state, which is likely not up-to-date.
> 
> [...]

Applied to kvm-x86 vmx, with a slight massaging of the docs as suggested by Hou.

[1/1] KVM: nVMX: Honor userspace MSR filter lists for nested VM-Enter/VM-Exit
      https://github.com/kvm-x86/linux/commit/653ea4489e69

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