linux-kernel - Re: [PATCH 2/3] KVM: nSVM: Propagate SVM_EXIT_CR0_SEL

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Message-ID: <aQupG93pUl-IYx8G@google.com>
Date: Wed, 5 Nov 2025 11:44:27 -0800
From: Sean Christopherson <seanjc@...gle.com>
To: Yosry Ahmed <yosry.ahmed@...ux.dev>
Cc: Paolo Bonzini <pbonzini@...hat.com>, Jim Mattson <jmattson@...gle.com>, kvm@...r.kernel.org, 
	linux-kernel@...r.kernel.org, stable@...r.kernel, 
	Matteo Rizzo <matteorizzo@...gle.com>
Subject: Re: [PATCH 2/3] KVM: nSVM: Propagate SVM_EXIT_CR0_SEL_WRITE correctly
 for LMSW emulation

On Fri, Oct 24, 2025, Yosry Ahmed wrote:
> When emulating L2 instructions, svm_check_intercept() checks whether a
> write to CR0 should trigger a synthesized #VMEXIT with
> SVM_EXIT_CR0_SEL_WRITE. For MOV-to-CR0, SVM_EXIT_CR0_SEL_WRITE is only
> triggered if any bit other than CR0.MP and CR0.TS is updated. However,
> according to the APM (24593—Rev.  3.42—March 2024, Table 15-7):
> 
>   The LMSW instruction treats the selective CR0-write
>   intercept as a non-selective intercept (i.e., it intercepts
>   regardless of the value being written).
> 
> Skip checking the changed bits for x86_intercept_lmsw and always inject
> SVM_EXIT_CR0_SEL_WRITE.
> 
> Fixes: cfec82cb7d31 ("KVM: SVM: Add intercept check for emulated cr accesses")
> Cc: stable@...r.kernel

Bad email (mostly in case you're using a macro for this; the next patch has the
same typo).