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[54.240.197.239]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-ab6e4a320d5sm723391266b.149.2025.02.03.01.15.06 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 03 Feb 2025 01:15:07 -0800 (PST) From: Paul Durrant X-Google-Original-From: Paul Durrant Message-ID: <2f4752d5-63ec-4e7f-bb7a-a97eecfdfb18@xen.org> Date: Mon, 3 Feb 2025 09:15:06 +0000 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Reply-To: paul@xen.org Subject: Re: [PATCH 3/5] KVM: x86/xen: Consult kvm_xen_enabled when checking for Xen MSR writes To: Sean Christopherson , Paolo Bonzini , David Woodhouse Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, syzbot+cdeaeec70992eca2d920@syzkaller.appspotmail.com, Joao Martins , David Woodhouse References: <20250201011400.669483-1-seanjc@google.com> <20250201011400.669483-4-seanjc@google.com> Content-Language: en-US Organization: Xen Project In-Reply-To: <20250201011400.669483-4-seanjc@google.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 01/02/2025 01:13, Sean Christopherson wrote: > Query kvm_xen_enabled when detecting writes to the Xen hypercall page MSR > so that the check is optimized away in the likely scenario that Xen isn't > enabled for the VM. > > Deliberately open code the check instead of using kvm_xen_msr_enabled() in > order to avoid a double load of xen_hvm_config.msr (which is admittedly > rather pointless given the widespread lack of READ_ONCE() usage on the > plethora of vCPU-scoped accesses to kvm->arch.xen state). > > No functional change intended. > > Signed-off-by: Sean Christopherson > --- > arch/x86/kvm/xen.h | 3 +++ > 1 file changed, 3 insertions(+) > Reviewed-by: Paul Durrant