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(p200300cfd70866e5a5d0fe9228997179.dip0.t-ipconnect.de. [2003:cf:d708:66e5:a5d0:fe92:2899:7179]) by smtp.gmail.com with ESMTPSA id d9-20020a5d6dc9000000b00327b5ca093dsm1893096wrz.117.2023.10.06.08.47.27 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 06 Oct 2023 08:47:27 -0700 (PDT) Message-ID: <2ba3ef6b-4af1-9c65-f542-bfcc8412e99c@redhat.com> Date: Fri, 6 Oct 2023 17:47:26 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.15.1 Subject: Re: [Virtio-fs] (no subject) Content-Language: en-US To: =?UTF-8?Q?Alex_Benn=c3=a9e?= Cc: "Michael S. Tsirkin" , virtio-fs@redhat.com, =?UTF-8?Q?Eugenio_P=c3=a9rez?= , Anton Kuchin , Yajun Wu , qemu-devel@nongnu.org References: <20231004125904.110781-1-hreitz@redhat.com> <20231004125904.110781-2-hreitz@redhat.com> <20231005170852.GB1342722@fedora> <20231005131352-mutt-send-email-mst@kernel.org> <00272da3-0a48-5544-6ba8-5dfde00be241@redhat.com> <20231006043518-mutt-send-email-mst@kernel.org> <20231006051802-mutt-send-email-mst@kernel.org> <20231006055229-mutt-send-email-mst@kernel.org> <87il7jg4oe.fsf@linaro.org> From: Hanna Czenczek In-Reply-To: <87il7jg4oe.fsf@linaro.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=170.10.133.124; envelope-from=hreitz@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -48 X-Spam_score: -4.9 X-Spam_bar: ---- X-Spam_report: (-4.9 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-2.797, RCVD_IN_DNSWL_NONE=-0.0001, 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: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On 06.10.23 17:17, Alex Bennée wrote: > Hanna Czenczek writes: > >> On 06.10.23 12:34, Michael S. Tsirkin wrote: >>> On Fri, Oct 06, 2023 at 11:47:55AM +0200, Hanna Czenczek wrote: >>>> On 06.10.23 11:26, Michael S. Tsirkin wrote: >>>>> On Fri, Oct 06, 2023 at 11:15:55AM +0200, Hanna Czenczek wrote: >>>>>> On 06.10.23 10:45, Michael S. Tsirkin wrote: >>>>>>> On Fri, Oct 06, 2023 at 09:48:14AM +0200, Hanna Czenczek wrote: >>>>>>>> On 05.10.23 19:15, Michael S. Tsirkin wrote: >>>>>>>>> On Thu, Oct 05, 2023 at 01:08:52PM -0400, Stefan Hajnoczi wrote: >>>>>>>>>> On Wed, Oct 04, 2023 at 02:58:57PM +0200, Hanna Czenczek wrote: > >>>> What I’m saying is, 923b8921d21 introduced SET_STATUS calls that broke all >>>> devices that would implement them as per virtio spec, and even today it’s >>>> broken for stateful devices.  The mentioned performance issue is likely >>>> real, but we can’t address it by making up SET_STATUS calls that are wrong. >>>> >>>> I concede that I didn’t think about DRIVER_OK.  Personally, I would do all >>>> final configuration that would happen upon a DRIVER_OK once the first vring >>>> is started (i.e. receives a kick).  That has the added benefit of being >>>> asynchronous because it doesn’t block any vhost-user messages (which are >>>> synchronous, and thus block downtime). >>>> >>>> Hanna >>> For better or worse kick is per ring. It's out of spec to start rings >>> that were not kicked but I guess you could do configuration ... >>> Seems somewhat asymmetrical though. >> I meant to take the first ring being started as the signal to do the >> global configuration, i.e. not do this once per vring, but once >> globally. >> >>> Let's wait until next week, hopefully Yajun Wu will answer. >> I mean, personally I don’t really care about the whole SET_STATUS >> thing.  It’s clear that it’s broken for stateful devices.  The fact >> that it took until 6f8be29ec17d to fix it for just any device that >> would implement it according to spec to me is a strong indication that >> nobody does implement it according to spec, and is currently only used >> to signal to some specific back-end that all rings have been set up >> and should be configured in a single block. > I'm certainly using [GS]ET_STATUS for the proposed F_TRANSPORT > extensions where everything is off-loaded to the vhost-user backend. How do these back-ends work with the fact that qemu uses SET_STATUS incorrectly when not offloading?  Do you plan on fixing that? (I.e. that we send SET_STATUS 0 when the VM is paused, potentially resetting state that is not recoverable, and that we set DRIVER and DRIVER_OK simultaneously.) Hanna