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Tue, 23 Jun 2020 09:55:37 -0400 X-MC-Unique: XVxuqKmzNPa5KRYIS7Y8mg-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 5985E464; Tue, 23 Jun 2020 13:55:36 +0000 (UTC) Received: from [10.36.110.7] (unknown [10.36.110.7]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 0236F619C0; Tue, 23 Jun 2020 13:55:34 +0000 (UTC) To: Matan Azrad , Xiao Wang Cc: "dev@dpdk.org" References: <1592497686-433697-1-git-send-email-matan@mellanox.com> <74f35cd8-3543-ba1c-0dc7-1502599e6cf7@redhat.com> <197079f4-7436-4f9e-7b8e-b8cb42042ffb@redhat.com> <62311463-2bc1-7f8b-1ec0-da31418e1d75@redhat.com> <6a2d8143-e48d-cdef-5b16-1c340d99b1ae@redhat.com> <3572c65c-394c-496f-483c-a57019550339@redhat.com> From: Maxime Coquelin Autocrypt: addr=maxime.coquelin@redhat.com; keydata= mQINBFOEQQIBEADjNLYZZqghYuWv1nlLisptPJp+TSxE/KuP7x47e1Gr5/oMDJ1OKNG8rlNg kLgBQUki3voWhUbMb69ybqdMUHOl21DGCj0BTU3lXwapYXOAnsh8q6RRM+deUpasyT+Jvf3a gU35dgZcomRh5HPmKMU4KfeA38cVUebsFec1HuJAWzOb/UdtQkYyZR4rbzw8SbsOemtMtwOx YdXodneQD7KuRU9IhJKiEfipwqk2pufm2VSGl570l5ANyWMA/XADNhcEXhpkZ1Iwj3TWO7XR uH4xfvPl8nBsLo/EbEI7fbuUULcAnHfowQslPUm6/yaGv6cT5160SPXT1t8U9QDO6aTSo59N jH519JS8oeKZB1n1eLDslCfBpIpWkW8ZElGkOGWAN0vmpLfdyiqBNNyS3eGAfMkJ6b1A24un /TKc6j2QxM0QK4yZGfAxDxtvDv9LFXec8ENJYsbiR6WHRHq7wXl/n8guyh5AuBNQ3LIK44x0 KjGXP1FJkUhUuruGyZsMrDLBRHYi+hhDAgRjqHgoXi5XGETA1PAiNBNnQwMf5aubt+mE2Q5r qLNTgwSo2dpTU3+mJ3y3KlsIfoaxYI7XNsPRXGnZi4hbxmeb2NSXgdCXhX3nELUNYm4ArKBP LugOIT/zRwk0H0+RVwL2zHdMO1Tht1UOFGfOZpvuBF60jhMzbQARAQABtCxNYXhpbWUgQ29x dWVsaW4gPG1heGltZS5jb3F1ZWxpbkByZWRoYXQuY29tPokCOAQTAQIAIgUCV3u/5QIbAwYL CQgHAwIGFQgCCQoLBBYCAwECHgECF4AACgkQyjiNKEaHD4ma2g/+P+Hg9WkONPaY1J4AR7Uf kBneosS4NO3CRy0x4WYmUSLYMLx1I3VH6SVjqZ6uBoYy6Fs6TbF6SHNc7QbB6Qjo3neqnQR1 71Ua1MFvIob8vUEl3jAR/+oaE1UJKrxjWztpppQTukIk4oJOmXbL0nj3d8dA2QgHdTyttZ1H xzZJWWz6vqxCrUqHU7RSH9iWg9R2iuTzii4/vk1oi4Qz7y/q8ONOq6ffOy/t5xSZOMtZCspu Mll2Szzpc/trFO0pLH4LZZfz/nXh2uuUbk8qRIJBIjZH3ZQfACffgfNefLe2PxMqJZ8mFJXc RQO0ONZvwoOoHL6CcnFZp2i0P5ddduzwPdGsPq1bnIXnZqJSl3dUfh3xG5ArkliZ/++zGF1O wvpGvpIuOgLqjyCNNRoR7cP7y8F24gWE/HqJBXs1qzdj/5Hr68NVPV1Tu/l2D1KMOcL5sOrz 2jLXauqDWn1Okk9hkXAP7+0Cmi6QwAPuBT3i6t2e8UdtMtCE4sLesWS/XohnSFFscZR6Vaf3 gKdWiJ/fW64L6b9gjkWtHd4jAJBAIAx1JM6xcA1xMbAFsD8gA2oDBWogHGYcScY/4riDNKXi lw92d6IEHnSf6y7KJCKq8F+Jrj2BwRJiFKTJ6ChbOpyyR6nGTckzsLgday2KxBIyuh4w+hMq TGDSp2rmWGJjASq5Ag0EVPSbkwEQAMkaNc084Qvql+XW+wcUIY+Dn9A2D1gMr2BVwdSfVDN7 0ZYxo9PvSkzh6eQmnZNQtl8WSHl3VG3IEDQzsMQ2ftZn2sxjcCadexrQQv3Lu60Tgj7YVYRM H+fLYt9W5YuWduJ+FPLbjIKynBf6JCRMWr75QAOhhhaI0tsie3eDsKQBA0w7WCuPiZiheJaL 4MDe9hcH4rM3ybnRW7K2dLszWNhHVoYSFlZGYh+MGpuODeQKDS035+4H2rEWgg+iaOwqD7bg CQXwTZ1kSrm8NxIRVD3MBtzp9SZdUHLfmBl/tLVwDSZvHZhhvJHC6Lj6VL4jPXF5K2+Nn/Su CQmEBisOmwnXZhhu8ulAZ7S2tcl94DCo60ReheDoPBU8PR2TLg8rS5f9w6mLYarvQWL7cDtT d2eX3Z6TggfNINr/RTFrrAd7NHl5h3OnlXj7PQ1f0kfufduOeCQddJN4gsQfxo/qvWVB7PaE 1WTIggPmWS+Xxijk7xG6x9McTdmGhYaPZBpAxewK8ypl5+yubVsE9yOOhKMVo9DoVCjh5To5 aph7CQWfQsV7cd9PfSJjI2lXI0dhEXhQ7lRCFpf3V3mD6CyrhpcJpV6XVGjxJvGUale7+IOp sQIbPKUHpB2F+ZUPWds9yyVxGwDxD8WLqKKy0WLIjkkSsOb9UBNzgRyzrEC9lgQ/ABEBAAGJ Ah8EGAECAAkFAlT0m5MCGwwACgkQyjiNKEaHD4nU8hAAtt0xFJAy0sOWqSmyxTc7FUcX+pbD KVyPlpl6urKKMk1XtVMUPuae/+UwvIt0urk1mXi6DnrAN50TmQqvdjcPTQ6uoZ8zjgGeASZg jj0/bJGhgUr9U7oG7Hh2F8vzpOqZrdd65MRkxmc7bWj1k81tOU2woR/Gy8xLzi0k0KUa8ueB iYOcZcIGTcs9CssVwQjYaXRoeT65LJnTxYZif2pfNxfINFzCGw42s3EtZFteczClKcVSJ1+L +QUY/J24x0/ocQX/M1PwtZbB4c/2Pg/t5FS+s6UB1Ce08xsJDcwyOPIH6O3tccZuriHgvqKP yKz/Ble76+NFlTK1mpUlfM7PVhD5XzrDUEHWRTeTJSvJ8TIPL4uyfzhjHhlkCU0mw7Pscyxn DE8G0UYMEaNgaZap8dcGMYH/96EfE5s/nTX0M6MXV0yots7U2BDb4soLCxLOJz4tAFDtNFtA wLBhXRSvWhdBJZiig/9CG3dXmKfi2H+wdUCSvEFHRpgo7GK8/Kh3vGhgKmnnxhl8ACBaGy9n fxjSxjSO6rj4/MeenmlJw1yebzkX8ZmaSi8BHe+n6jTGEFNrbiOdWpJgc5yHIZZnwXaW54QT UhhSjDL1rV2B4F28w30jYmlRmm2RdN7iCZfbyP3dvFQTzQ4ySquuPkIGcOOHrvZzxbRjzMx1 Mwqu3GQ= Message-ID: <7c6bd0b2-8657-3c34-ab1f-f397c39ea2ec@redhat.com> Date: Tue, 23 Jun 2020 15:55:33 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 MIME-Version: 1.0 In-Reply-To: Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Subject: Re: [dpdk-dev] [PATCH v1 3/4] vhost: improve device ready definition X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" Hi Matan, On 6/23/20 1:53 PM, Matan Azrad wrote: > > > From: Maxime Coquelin: >> On 6/23/20 11:02 AM, Matan Azrad wrote: >>> >>> >>> From: Maxime Coquelin: >>>> On 6/22/20 5:51 PM, Matan Azrad wrote: >>>>> >>>>> >>>>> From: Maxime Coquelin: >>>>>> On 6/22/20 3:43 PM, Matan Azrad wrote: >>>>>>> >>>>>>> >>>>>>> From: Maxime Coquelin: >>>>>>>> Sent: Monday, June 22, 2020 3:33 PM >>>>>>>> To: Matan Azrad ; Xiao Wang >>>>>>>> >>>>>>>> Cc: dev@dpdk.org >>>>>>>> Subject: Re: [PATCH v1 3/4] vhost: improve device ready >>>>>>>> definition >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> On 6/22/20 12:06 PM, Matan Azrad wrote: >>>>>>>>> >>>>>>>>> Hi Maxime >>>>>>>>> >>>>>>>>> From: Maxime Coquelin >>>>>>>>>> Sent: Monday, June 22, 2020 11:56 AM >>>>>>>>>> To: Matan Azrad ; Xiao Wang >>>>>>>>>> >>>>>>>>>> Cc: dev@dpdk.org >>>>>>>>>> Subject: Re: [PATCH v1 3/4] vhost: improve device ready >>>>>>>>>> definition >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> On 6/22/20 10:41 AM, Matan Azrad wrote: >>>>>>>>>>>> The issue is if you only check ready state only before and >>>>>>>>>>>> after the message affecting the ring is handled, it can be >>>>>>>>>>>> ready at both stages, while the rings have changed and state >>>>>>>>>>>> change callback should >>>>>>>>>> have been called. >>>>>>>>>>> But in this version I checked twice, before message handler >>>>>>>>>>> and after >>>>>>>>>> message handler, so it should catch any update. >>>>>>>>>> >>>>>>>>>> No, this is not enough, we have to check also during some >>>>>>>>>> handlers, so that the ready state is invalidated because >>>>>>>>>> sometimes it will be ready before and after the message handler >>>>>>>>>> but >>>> with different values. >>>>>>>>>> >>>>>>>>>> That's what I did in my example patch: >>>>>>>>>> @@ -1847,15 +1892,16 @@ vhost_user_set_vring_kick(struct >>>>>> virtio_net >>>>>>>>>> **pdev, struct VhostUserMsg *msg, >>>>>>>>>> >>>>>>>>>> ... >>>>>>>>>> >>>>>>>>>> if (vq->kickfd >= 0) >>>>>>>>>> close(vq->kickfd); >>>>>>>>>> + >>>>>>>>>> + vq->kickfd = VIRTIO_UNINITIALIZED_EVENTFD; >>>>>>>>>> + >>>>>>>>>> + vhost_user_update_vring_state(dev, file.index); >>>>>>>>>> + >>>>>>>>>> vq->kickfd = file.fd; >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> Without that, the ready check will return ready before and >>>>>>>>>> after the kickfd changed and the driver won't be notified. >>>>>>>>> >>>>>>>>> The driver will be notified in the next >>>>>>>>> VHOST_USER_SET_VRING_ENABLE >>>>>>>> message according to v1. >>>>>>>>> >>>>>>>>> One of our assumption we agreed on in the design mail is that it >>>>>>>>> doesn't >>>>>>>> make sense that QEMU will change queue configuration without >>>>>>>> enabling the queue again. >>>>>>>>> Because of that we decided to force calling state callback again >>>>>>>>> when >>>>>>>> QEMU send VHOST_USER_SET_VRING_ENABLE(1) message even if >> the >>>>>> queue is >>>>>>>> already ready. >>>>>>>>> So when driver/app see state enable->enable, it should take into >>>>>>>>> account >>>>>>>> that the queue configuration was probably changed. >>>>>>>>> >>>>>>>>> I think that this assumption is correct according to the QEMU code. >>>>>>>> >>>>>>>> Yes, this was our initial assumption. >>>>>>>> But now looking into the details of the implementation, I find it >>>>>>>> is even cleaner & clearer not to do this assumption. >>>>>>>> >>>>>>>>> That's why I prefer to collect all the ready checks callbacks >>>>>>>>> (queue state and >>>>>>>> device new\conf) to one function that will be called after the >>>>>>>> message >>>>>>>> handler: >>>>>>>>> Pseudo: >>>>>>>>> vhost_user_update_ready_statuses() { >>>>>>>>> switch (msg): >>>>>>>>> case enable: >>>>>>>>> if(enable is 1) >>>>>>>>> force queue state =1. >>>>>>>>> case callfd >>>>>>>>> case kickfd >>>>>>>>> ..... >>>>>>>>> Check queue and device ready + call callbacks if >> needed.. >>>>>>>>> Default >>>>>>>>> Return; >>>>>>>>> } >>>>>>>> >>>>>>>> I find it more natural to "invalidate" ready state where it is >>>>>>>> handled (after vring_invalidate(), before setting new FD for call >>>>>>>> & kick, ...) >>>>>>> >>>>>>> I think that if you go with this direction, if the first queue >>>>>>> pair is invalidated, >>>>>> you need to notify app\driver also about device ready change. >>>>>>> Also it will cause 2 notifications to the driver instead of one in >>>>>>> case of FD >>>>>> change. >>>>>> >>>>>> You'll always end-up with two notifications, either Qemu has sent >>>>>> the disable and so you'll have one notification for the disable and >>>>>> one for the enable, or it didn't sent the disable and it will >>>>>> happen at old value invalidation time and after new value is taken into >> account. >>>>>> >>>>> >>>>> I don't see it in current QEMU behavior. >>>>> When working MQ I see that some virtqs get configuration message >>>>> while >>>> they are in enabled state. >>>>> Then, enable message is sent again later. >>>> >>>> I guess you mean the first queue pair? And it would not be in ready >>>> state as it would be the initial configuration of the queue? >>> >>> Even after initialization when queue is ready. >>> >>>>> >>>>>>> Why not to take this correct assumption and update ready state >>>>>>> only in one >>>>>> point in the code instead of doing it in all the configuration >>>>>> handlers >>>> around? >>>>>>> IMO, It is correct, less intrusive, simpler, clearer and cleaner. >>>>>> >>>>>> I just looked closer at the Vhost-user spec, and I'm no more so >>>>>> sure this is a correct assumption: >>>>>> >>>>>> "While processing the rings (whether they are enabled or not), >>>>>> client must support changing some configuration aspects on the fly." >>>>> >>>>> Ok, this doesn't explain how configuration is changed on the fly. >>>> >>>> I agree it lacks a bit of clarity. >>>> >>>>> As I mentioned, QEMU sends enable message always after configuration >>>> message. >>>> >>>> Yes, but we should not do assumptions on current Qemu version when >>>> possible. Better to be safe and follow the specification, it will be more >> robust. >>>> There is also the Virtio-user PMD to take into account for example. >>> >>> I understand your point here but do you really want to be ready for any >> configuration update in run time? >>> What does it mean? How datatpath should handle configuration from >> control thread in run time while traffic is on? >>> For example, changing queue size \ addresses must stop traffic before... >>> Also changing FDs is very sensitive. >>> >>> It doesn't make sense to me. >>> >>> Also, according to "on the fly" direction we should not disable the queue >> unless enable message is coming to disable it. > > No response, so looks like you agree that it doesn't make sense. No, my reply was general to all your comments. With SW backend, I agree we don't need to disable the rings in case of asynchronous changes to the ring because we protect it with a lock, so we are sure the ring won't be accessed by another thread while doing the change. For vDPA case that's more problematic because we have no such locking mechanism. For example memory hotplug, Qemu does not seem to disable the queues so we need to stop the vDPA device one way or another so that it does not process the rings while the Vhost lib remaps the memory areas. >>> In addition: >>> Do you really want to toggle vDPA drivers\app for any configuration >> message? It may cause queue recreation for each one (at least for mlx5). >> >> I want to have something robust and maintainable. > > Me too. > >> These messages arriving after a queue have been configured once are rare >> events, but this is usually the kind of things that cause maintenance burden. > > In case of guest poll mode (testpmd virtio) we all the time get callfd twice. Right. >> If you look at my example patch, you will understand that with my proposal, >> there won't be any more state change notification than with your proposal >> when Qemu or any other Vhost-user master send a disable request before >> sending the request that impact the queue state. > > we didn't talk about disable time - this one is very simple. > > Yes, In case the queue is disabled your proposal doesn't send extra notification as my. > But in case the queue is ready, your proposal send extra not ready notification for kikfd,callfd,set_vring_base configurations. I think this is necessary for synchronization with the Vhost-user master (in case the master asks for this synchronization, like set_mem_table for instance when reply-ack is enabled). >> It just adds more robustness if this unlikely event happens, by invalidating >> the ring state to not ready before doing the actual ring configuration change. >> So that this config change is not missed by the vDPA driver or the application. > > One more issue here is that there is some time that device is ready (already configured) and the first vittq-pair is not ready (your invalidate proposal for set_vring_base). > It doesn’t save the concept that device is ready only in case the first virtq-pair is ready. I understand the spec as "the device is ready as soon as the first queue pair is ready", but I might be wrong. Do you suggest to call the dev_close() vDPA callback and the destroy_device() application callback as soon as one of the ring of the first queue pair receive a disable request or, with my patch, when one of the rings receives a request that changes the ring state? > > I will not insist anymore on waiting for enable for notifying although I not fan with it. > > So, I suggest to create 1 notification function to be called after message handler and before reply. > This function is the only one which notify ready states in the next options: > > 1. virtq ready state is changed in the queue. > 2. virtq ready state stays on after configuration message handler. > 3. device state will be enabled when the first queue pair is ready. IIUC, it will not disable the queues when there is a state change, is that correct? If so, I think it does not work with memory hotplug case I mentioned earlier. Even for the callfd double change it can be problematic as Vhost-lib will close the first one while it will still be used by the driver (Btw, I see my example patch is also buggy in this regards, it should reset the call_fd value in the virtqueue, then call vhost_user_update_vring_state() and finally close the FD). Thanks, Maxime > > Matan > > > >> Maxime >