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([2001:b07:6468:f312:e4f4:3c00:2b79:d6dc]) by smtp.gmail.com with ESMTPSA id b82sm972243wmb.46.2020.03.25.17.28.03 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 25 Mar 2020 17:28:04 -0700 (PDT) Subject: Re: [PATCH] KVM: LAPIC: Also cancel preemption timer when disarm LAPIC timer To: Wanpeng Li Cc: LKML , kvm , Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel References: <1585031530-19823-1-git-send-email-wanpengli@tencent.com> <708f1914-be5e-91a0-2fdf-8d34b78ca7da@redhat.com> From: Paolo Bonzini Message-ID: <5582f554-5ae9-4cb9-d8e9-f1ff57fca35c@redhat.com> Date: Thu, 26 Mar 2020 01:28:03 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 26/03/20 01:20, Wanpeng Li wrote: >> There are a few other occurrences of hrtimer_cancel, and all of them >> probably have a similar issue. What about adding a cancel_apic_timer > Other places are a little different, here we just disarm the timer, > other places we will restart the timer just after the disarm except > the vCPU reset (fixed in commit 95c065400a1 (KVM: VMX: Stop the > preemption timer during vCPU reset)), the restart will override > vmx->hv_deadline_tsc. What do you think? I can do it if introduce > cancel_apic_timer() is still better. At least start_apic_timer() would benefit from adding hrtimer_cancel(), removing it from kvm_set_lapic_tscdeadline_msr and kvm_lapic_reg_write. But you're right that it doesn't benefit from a cancel_apic_timer(), because ultimately they either update the preemption timer or cancel it in start_sw_timer. So I'll apply your patch and send a cleanup myself for start_apic_timer. Thanks, Paolo