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([2001:b07:6468:f312:5e2c:eb9a:a8b6:fd3e]) by smtp.googlemail.com with ESMTPSA id r27-20020a056402035b00b0043c92c44c53sm6053094edw.93.2022.08.09.07.32.00 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 09 Aug 2022 07:32:03 -0700 (PDT) Message-ID: <953d2e99-ed1a-384d-6d3a-0f656a243f82@redhat.com> Date: Tue, 9 Aug 2022 16:31:59 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.12.0 Subject: Re: [PATCH v3 2/2] KVM: x86/xen: Stop Xen timer before changing IRQ Content-Language: en-US To: David Woodhouse , Sean Christopherson Cc: Coleman Dietsch , kvm@vger.kernel.org, Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H . Peter Anvin" , linux-kernel@vger.kernel.org, skhan@linuxfoundation.org, Pavel Skripkin , linux-kernel-mentees@lists.linuxfoundation.org, stable@vger.kernel.org, syzbot+e54f930ed78eb0f85281@syzkaller.appspotmail.com, metikaya References: <20220808190607.323899-2-dietschc@csp.edu> <20220808190607.323899-3-dietschc@csp.edu> <43e258cc-71ac-bde4-d1f8-9eb9519928d3@redhat.com> <4fc1371b83001b4eed1617c37bec6b9d007e45c2.camel@infradead.org> <0b5dcab333906f166fcdbc296373cc5e08bec79f.camel@infradead.org> From: Paolo Bonzini In-Reply-To: <0b5dcab333906f166fcdbc296373cc5e08bec79f.camel@infradead.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 8/9/22 16:16, David Woodhouse wrote: > I find the new version a bit harder to follow, with its init-then-stop- > then-start logic: > > case KVM_XEN_VCPU_ATTR_TYPE_TIMER: > if (data->u.timer.port && > data->u.timer.priority != KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL) { > r = -EINVAL; > break; > } > > if (!vcpu->arch.xen.timer.function) > kvm_xen_init_timer(vcpu); > > /* Stop the timer (if it's running) before changing the vector */ > kvm_xen_stop_timer(vcpu); > vcpu->arch.xen.timer_virq = data->u.timer.port; I think this is fine, if anything the kvm_xen_stop_timer() call could be placed in an "else" but I'm leaning towards applying this version of the patch. Paolo