linux-kernel - Re: [PATCH 12/28] KVM: SVM: Implement and adopt VMX style MSR intercepts APIs

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Message-ID: <aEFTE1oZ/zvzXiTT@intel.com>
Date: Thu, 5 Jun 2025 16:19:31 +0800
From: Chao Gao <chao.gao@...el.com>
To: Sean Christopherson <seanjc@...gle.com>
CC: Paolo Bonzini <pbonzini@...hat.com>, <kvm@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, Borislav Petkov <bp@...en8.de>, Xin Li
	<xin@...or.com>, Dapeng Mi <dapeng1.mi@...ux.intel.com>
Subject: Re: [PATCH 12/28] KVM: SVM: Implement and adopt VMX style MSR
 intercepts APIs

On Thu, May 29, 2025 at 04:39:57PM -0700, Sean Christopherson wrote:
>Add and use SVM MSR interception APIs (in most paths) to match VMX's
>APIs and nomenclature.  Specifically, add SVM variants of:
>
>        vmx_disable_intercept_for_msr(vcpu, msr, type)
>        vmx_enable_intercept_for_msr(vcpu, msr, type)
>        vmx_set_intercept_for_msr(vcpu, msr, type, intercept)
>
>to eventually replace SVM's single helper:
>
>        set_msr_interception(vcpu, msrpm, msr, allow_read, allow_write)
>
>which is awkward to use (in all cases, KVM either applies the same logic
>for both reads and writes, or intercepts one of read or write), and is
>unintuitive due to using '0' to indicate interception should be *set*.
>
>Keep the guts of the old API for the moment to avoid churning the MSR
>filter code, as that mess will be overhauled in the near future.  Leave
>behind a temporary comment to call out that the shadow bitmaps have
>inverted polarity relative to the bitmaps consumed by hardware.
>
>No functional change intended.
>
>Signed-off-by: Sean Christopherson <seanjc@...gle.com>

Reviewed-by: Chao Gao <chao.gao@...el.com>

two nits below:

>+void svm_disable_intercept_for_msr(struct kvm_vcpu *vcpu, u32 msr, int type)
> {
>-	set_shadow_msr_intercept(vcpu, msr, read, write);
>-	set_msr_interception_bitmap(vcpu, msrpm, msr, read, write);
>+	struct vcpu_svm *svm = to_svm(vcpu);
>+	void *msrpm = svm->msrpm;
>+
>+	/* Note, the shadow intercept bitmaps have inverted polarity. */
>+	set_shadow_msr_intercept(vcpu, msr, type & MSR_TYPE_R, type & MSR_TYPE_W);
>+
>+	/*
>+	 * Don't disabled interception for the MSR if userspace wants to

s/disabled/disable

<snip>

>+void svm_enable_intercept_for_msr(struct kvm_vcpu *vcpu, u32 msr, int type)
>+{
>+	struct vcpu_svm *svm = to_svm(vcpu);
>+	void *msrpm = svm->msrpm;
>+
>+

Remove one newline here.