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([2001:b07:6468:f312:c8dd:75d4:99ab:290a]) by smtp.gmail.com with ESMTPSA id n10sm4629856wro.39.2021.02.11.03.40.55 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 11 Feb 2021 03:40:55 -0800 (PST) Subject: Re: [PATCH] virtio: disable ioeventfd for record/replay To: =?UTF-8?Q?Alex_Benn=c3=a9e?= , Pavel Dovgalyuk References: <161303249335.948571.16873882207700527766.stgit@pasha-ThinkPad-X280> <875z2zugai.fsf@linaro.org> From: Paolo Bonzini Message-ID: Date: Thu, 11 Feb 2021 12:40:54 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: <875z2zugai.fsf@linaro.org> Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=pbonzini@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=216.205.24.124; envelope-from=pbonzini@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -35 X-Spam_score: -3.6 X-Spam_bar: --- X-Spam_report: (-3.6 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.568, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.211, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: qemu-devel@nongnu.org, mst@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 11/02/21 09:58, Alex Bennée wrote: >> virtio devices support separate iothreads waiting for >> events from file descriptors. These are asynchronous >> events that can't be recorded and replayed, therefore >> this patch disables ioeventfd for all devices when >> record or replay is enabled. > Does it always have to be the case? Can a virtio device forgo iothreads > and poll events from the main loop? Yes and in fact it's the default, but ioeventfd has the same issue I think even if the polling happens from the main thread. Paolo