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([2001:b07:6468:f312:f43b:97b2:4c89:7446]) by smtp.gmail.com with ESMTPSA id a24sm6542275wmb.24.2020.04.22.01.38.39 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 22 Apr 2020 01:38:40 -0700 (PDT) Subject: Re: [PATCH 1/2] KVM: X86: TSCDEADLINE MSR emulation fastpath To: Wanpeng Li Cc: LKML , kvm , Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , Haiwei Li References: <1587468026-15753-1-git-send-email-wanpengli@tencent.com> <1587468026-15753-2-git-send-email-wanpengli@tencent.com> From: Paolo Bonzini Message-ID: Date: Wed, 22 Apr 2020 10:38:39 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 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 22/04/20 02:48, Wanpeng Li wrote: > On Tue, 21 Apr 2020 at 19:37, Paolo Bonzini wrote: >> On 21/04/20 13:20, Wanpeng Li wrote: >>> + case MSR_IA32_TSCDEADLINE: >>> + if (!kvm_x86_ops.event_needs_reinjection(vcpu)) { >>> + data = kvm_read_edx_eax(vcpu); >>> + if (!handle_fastpath_set_tscdeadline(vcpu, data)) >>> + ret = EXIT_FASTPATH_CONT_RUN; >>> + } >>> break; >> Can you explain the event_needs_reinjection case? Also, does this break > This is used to catch the case vmexit occurred while another event was > being delivered to guest software, I move the > vmx_exit_handlers_fastpath() call after vmx_complete_interrupts() > which will decode such event and make kvm_event_needs_reinjection > return true. This doesn't need a callback, kvm_event_needs_reinjection should be enough. You should also check other conditions such as vcpu->mode == EXITING_GUEST_MODE || kvm_request_pending(vcpu) || need_resched() || signal_pending(current) before doing CONT_RUN. >> AMD which does not implement the callback? > Now I add the tscdeadline msr emulation and vmx-preemption timer > fastpath pair for Intel platform. But this would cause a crash if you run on AMD. Paolo