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[81.97.203.96]) by smtp.gmail.com with ESMTPSA id bu9-20020a056000078900b002be1dcb6efbsm9066028wrb.9.2023.01.19.11.48.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 19 Jan 2023 11:48:14 -0800 (PST) Date: Thu, 19 Jan 2023 19:48:12 +0000 From: "Dr. David Alan Gilbert" To: Greg Kurz Cc: Maxime Coquelin , Yajun Wu , Laurent Vivier , Stefan Hajnoczi , "qemu-devel@nongnu.org" , Peter Maydell , Parav Pandit , "Michael S. Tsirkin" Subject: Re: [PULL v4 76/83] vhost-user: Support vhost_dev_start Message-ID: References: <20221107224600.934080-1-mst@redhat.com> <20221107224600.934080-77-mst@redhat.com> <43145ede-89dc-280e-b953-6a2b436de395@redhat.com> <20230109054633-mutt-send-email-mst@kernel.org> <31f87c1d-9cce-6507-8e90-4d7942d7dc54@redhat.com> <1cb334f0-d495-45f8-564e-4093746850d6@redhat.com> <20230117131257.231473d4@bahia> <20230117133645.78c5d8a8@bahia> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230117133645.78c5d8a8@bahia> User-Agent: Mutt/2.2.9 (2022-11-12) Received-SPF: pass client-ip=170.10.133.124; envelope-from=dgilbert@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 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, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-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 * Greg Kurz (groug@kaod.org) wrote: > On Tue, 17 Jan 2023 13:12:57 +0100 > Greg Kurz wrote: > > > Hi Maxime, > > > > On Tue, 17 Jan 2023 10:49:37 +0100 > > Maxime Coquelin wrote: > > > > > Hi Yajun, > > > > > > On 1/16/23 08:14, Yajun Wu wrote: > > > > Not quite sure about the whole picture. > > > > > > > > Seems while qemu waiting response of vhost_user_get_status, dpdk send out VHOST_USER_SLAVE_IOTLB_MSG and trigger qemu function vhost_backend_update_device_iotlb. > > > > Qemu wait on reply of VHOST_USER_IOTLB_MSG but get VHOST_USER_GET_STATUS reply. > > > > > > Thanks for the backtrace, that helps a lot. > > > > > > The issue happens because: > > > 1. Introduction of nested event loop in vhost_user_read() [0] features > > > that enables handling slave channel request while waiting for reply on > > > the masyer channel. > > > 2. Slave VHOST_USER_SLAVE_IOTLB_MSG slave request handling ends-up > > > sending a VHOST_USER_IOTLB_MSG on the master channel. > > > > > > So while waiting for VHOST_USER_IOTLB_MSG reply, it receives the reply > > > for the first request sent on the master channel, here the > > > VHOST_USER_GET_STATUS reply. > > > > > > I don't see an easy way to fix it. > > > > > > One option would be to have the slave channel being handled by another > > > thread, and protect master channel with a lock to enforce the > > > synchronization. But this may induce other issues, so that's not a light > > > change. > > > > > > > This is going to be tough because the back-end might have set the > > VHOST_USER_NEED_REPLY_MASK flag on the VHOST_USER_SLAVE_IOTLB_MSG > > request and thus might be waiting for a response on the slave > > channel. In order to emit such a response, the front-end must > > send VHOST_USER_SLAVE_IOTLB_MSG updates on the master channel *first* > > according to the protocol specification. This means that we really > > cannot handle VHOST_USER_SLAVE_IOTLB_MSG requests while there's > > an on-going transaction on the master channel. > > > > > (Adding Greg and Stefan, who worked on the nested event loop series.) > > > > > > Simply reverting nested event loop support may not be an option, since > > > it would break virtiofsd, as if my understanding is correct, waits for > > > some slave channel request to complete in order to complete a request > > > made by QEMU on the master channel. > > > > > > Any thougths? > > > > > > > Well... the nested even loop was added as preparatory work for "the > > upcoming enablement of DAX with virtio-fs". This requires changes on > > the QEMU side that haven't been merged yet. Technically, it seems that > > reverting the nested event loop won't break anything in upstream QEMU > > at this point (but this will bite again as soon as DAX enablement gets > > merged). > > > > Cc'ing Dave to know about the DAX enablement status. Yeh not too much to say; but having just sent the patches to nuke the C virtiofsd, the plan is to look at the Rust daemon; it's got code in already for DAX, and apparently working with CrosVM which I believe are based on my original proposals for the protocol. But it would probably need a clean fix to this deadlock. IMHO the slave channel needs properly specifying; no one really understands what the semantics are supposed to be. Dave > > AFAIK the event loop is only needed for the VHOST_USER_GET_VRING_BASE > > message. Another possibility might be to create the nested event loop > > in this case only : this would allow VHOST_USER_GET_STATUS to complete > > before QEMU starts processing the VHOST_USER_SLAVE_IOTLB_MSG requests. > > > > Cheers, > > > > -- > > Greg > > > > > Maxime > > > > > > [0]: > > > https://patchwork.ozlabs.org/project/qemu-devel/patch/20210312092212.782255-6-groug@kaod.org/ > > > > > > > > > > Break on first error message("Received unexpected msg type. Expected 22 received 40") > > > > > > > > #0 0x0000555555b72ed4 in process_message_reply (dev=0x5555584dd600, msg=0x7fffffffa330) at ../hw/virtio/vhost-user.c:445 > > > > #1 0x0000555555b77c26 in vhost_user_send_device_iotlb_msg (dev=0x5555584dd600, imsg=0x7fffffffa600) at ../hw/virtio/vhost-user.c:2341 > > > > #2 0x0000555555b7179e in vhost_backend_update_device_iotlb (dev=0x5555584dd600, iova=10442706944, uaddr=140736119902208, len=4096, perm=IOMMU_RW) at ../hw/virtio/vhost-backend.c:361 > > > > #3 0x0000555555b6e34c in vhost_device_iotlb_miss (dev=0x5555584dd600, iova=10442706944, write=1) at ../hw/virtio/vhost.c:1113 > > > > #4 0x0000555555b718d9 in vhost_backend_handle_iotlb_msg (dev=0x5555584dd600, imsg=0x7fffffffa7b0) at ../hw/virtio/vhost-backend.c:393 > > > > #5 0x0000555555b76144 in slave_read (ioc=0x555557a38680, condition=G_IO_IN, opaque=0x5555584dd600) at ../hw/virtio/vhost-user.c:1726 > > > > #6 0x0000555555c797a5 in qio_channel_fd_source_dispatch (source=0x555556a06fb0, callback=0x555555b75f86 , user_data=0x5555584dd600) at ../io/channel-watch.c:84 > > > > #7 0x00007ffff554895d in g_main_context_dispatch () at /lib64/libglib-2.0.so.0 > > > > #8 0x00007ffff5548d18 in g_main_context_iterate.isra () at /lib64/libglib-2.0.so.0 > > > > #9 0x00007ffff5549042 in g_main_loop_run () at /lib64/libglib-2.0.so.0 > > > > #10 0x0000555555b72de7 in vhost_user_read (dev=0x5555584dd600, msg=0x7fffffffac50) at ../hw/virtio/vhost-user.c:413 > > > > #11 0x0000555555b72e9b in process_message_reply (dev=0x5555584dd600, msg=0x7fffffffaf10) at ../hw/virtio/vhost-user.c:439 > > > > #12 0x0000555555b77c26 in vhost_user_send_device_iotlb_msg (dev=0x5555584dd600, imsg=0x7fffffffb1e0) at ../hw/virtio/vhost-user.c:2341 > > > > #13 0x0000555555b7179e in vhost_backend_update_device_iotlb (dev=0x5555584dd600, iova=10468392960, uaddr=140736145588224, len=4096, perm=IOMMU_RW) at ../hw/virtio/vhost-backend.c:361 > > > > #14 0x0000555555b6e34c in vhost_device_iotlb_miss (dev=0x5555584dd600, iova=10468392960, write=1) at ../hw/virtio/vhost.c:1113 > > > > #15 0x0000555555b718d9 in vhost_backend_handle_iotlb_msg (dev=0x5555584dd600, imsg=0x7fffffffb390) at ../hw/virtio/vhost-backend.c:393 > > > > #16 0x0000555555b76144 in slave_read (ioc=0x555557a38680, condition=G_IO_IN, opaque=0x5555584dd600) at ../hw/virtio/vhost-user.c:1726 > > > > #17 0x0000555555c797a5 in qio_channel_fd_source_dispatch (source=0x555556c70250, callback=0x555555b75f86 , user_data=0x5555584dd600) at ../io/channel-watch.c:84 > > > > #18 0x00007ffff554895d in g_main_context_dispatch () at /lib64/libglib-2.0.so.0 > > > > #19 0x00007ffff5548d18 in g_main_context_iterate.isra () at /lib64/libglib-2.0.so.0 > > > > #20 0x00007ffff5549042 in g_main_loop_run () at /lib64/libglib-2.0.so.0 > > > > #21 0x0000555555b72de7 in vhost_user_read (dev=0x5555584dd600, msg=0x7fffffffb830) at ../hw/virtio/vhost-user.c:413 > > > > #22 0x0000555555b72e9b in process_message_reply (dev=0x5555584dd600, msg=0x7fffffffbaf0) at ../hw/virtio/vhost-user.c:439 > > > > #23 0x0000555555b77c26 in vhost_user_send_device_iotlb_msg (dev=0x5555584dd600, imsg=0x7fffffffbdc0) at ../hw/virtio/vhost-user.c:2341 > > > > #24 0x0000555555b7179e in vhost_backend_update_device_iotlb (dev=0x5555584dd600, iova=10442702848, uaddr=140736119898112, len=4096, perm=IOMMU_RW) at ../hw/virtio/vhost-backend.c:361 > > > > #25 0x0000555555b6e34c in vhost_device_iotlb_miss (dev=0x5555584dd600, iova=10442702848, write=1) at ../hw/virtio/vhost.c:1113 > > > > #26 0x0000555555b718d9 in vhost_backend_handle_iotlb_msg (dev=0x5555584dd600, imsg=0x7fffffffbf70) at ../hw/virtio/vhost-backend.c:393 > > > > #27 0x0000555555b76144 in slave_read (ioc=0x555557a38680, condition=G_IO_IN, opaque=0x5555584dd600) at ../hw/virtio/vhost-user.c:1726 > > > > #28 0x0000555555c797a5 in qio_channel_fd_source_dispatch (source=0x555556f1a530, callback=0x555555b75f86 , user_data=0x5555584dd600) at ../io/channel-watch.c:84 > > > > #29 0x00007ffff554895d in g_main_context_dispatch () at /lib64/libglib-2.0.so.0 > > > > #30 0x00007ffff5548d18 in g_main_context_iterate.isra () at /lib64/libglib-2.0.so.0 > > > > #31 0x00007ffff5549042 in g_main_loop_run () at /lib64/libglib-2.0.so.0 > > > > #32 0x0000555555b72de7 in vhost_user_read (dev=0x5555584dd600, msg=0x7fffffffc420) at ../hw/virtio/vhost-user.c:413 > > > > #33 0x0000555555b754b1 in vhost_user_get_u64 (dev=0x5555584dd600, request=40, u64=0x7fffffffc6e0) at ../hw/virtio/vhost-user.c:1349 > > > > #34 0x0000555555b758ff in vhost_user_get_status (dev=0x5555584dd600, status=0x7fffffffc713 "W\020") at ../hw/virtio/vhost-user.c:1474 > > > > #35 0x0000555555b75967 in vhost_user_add_status (dev=0x5555584dd600, status=7 '\a') at ../hw/virtio/vhost-user.c:1488 > > > > #36 0x0000555555b78bf6 in vhost_user_dev_start (dev=0x5555584dd600, started=true) at ../hw/virtio/vhost-user.c:2758 > > > > #37 0x0000555555b709ad in vhost_dev_start (hdev=0x5555584dd600, vdev=0x555557b965d0, vrings=false) at ../hw/virtio/vhost.c:1988 > > > > #38 0x000055555584291c in vhost_net_start_one (net=0x5555584dd600, dev=0x555557b965d0) at ../hw/net/vhost_net.c:271 > > > > #39 0x0000555555842f1e in vhost_net_start (dev=0x555557b965d0, ncs=0x555557bc09e0, data_queue_pairs=1, cvq=0) at ../hw/net/vhost_net.c:412 > > > > #40 0x0000555555b1bf61 in virtio_net_vhost_status (n=0x555557b965d0, status=15 '\017') at ../hw/net/virtio-net.c:311 > > > > #41 0x0000555555b1c20c in virtio_net_set_status (vdev=0x555557b965d0, status=15 '\017') at ../hw/net/virtio-net.c:392 > > > > #42 0x0000555555b1ed04 in virtio_net_handle_mq (n=0x555557b965d0, cmd=0 '\000', iov=0x555556c7ef50, iov_cnt=1) at ../hw/net/virtio-net.c:1497 > > > > #43 0x0000555555b1eef0 in virtio_net_handle_ctrl_iov (vdev=0x555557b965d0, in_sg=0x555556a09880, in_num=1, out_sg=0x555556a09890, out_num=1) at ../hw/net/virtio-net.c:1534 > > > > #44 0x0000555555b1efe9 in virtio_net_handle_ctrl (vdev=0x555557b965d0, vq=0x7fffc04ac140) at ../hw/net/virtio-net.c:1557 > > > > #45 0x0000555555b63776 in virtio_queue_notify_vq (vq=0x7fffc04ac140) at ../hw/virtio/virtio.c:2249 > > > > #46 0x0000555555b669dc in virtio_queue_host_notifier_read (n=0x7fffc04ac1b4) at ../hw/virtio/virtio.c:3529 > > > > #47 0x0000555555e3f458 in aio_dispatch_handler (ctx=0x555556a016c0, node=0x7ffd8800e430) at ../util/aio-posix.c:369 > > > > #48 0x0000555555e3f613 in aio_dispatch_handlers (ctx=0x555556a016c0) at ../util/aio-posix.c:412 > > > > #49 0x0000555555e3f669 in aio_dispatch (ctx=0x555556a016c0) at ../util/aio-posix.c:422 > > > > #50 0x0000555555e585de in aio_ctx_dispatch (source=0x555556a016c0, callback=0x0, user_data=0x0) at ../util/async.c:321 > > > > #51 0x00007ffff554895d in g_main_context_dispatch () at /lib64/libglib-2.0.so.0 > > > > #52 0x0000555555e5abea in glib_pollfds_poll () at ../util/main-loop.c:295 > > > > #53 0x0000555555e5ac64 in os_host_main_loop_wait (timeout=0) at ../util/main-loop.c:318 > > > > #54 0x0000555555e5ad69 in main_loop_wait (nonblocking=0) at ../util/main-loop.c:604 > > > > #55 0x00005555559693de in qemu_main_loop () at ../softmmu/runstate.c:731 > > > > #56 0x00005555556e7c06 in qemu_default_main () at ../softmmu/main.c:37 > > > > #57 0x00005555556e7c3c in main (argc=71, argv=0x7fffffffcda8) at ../softmmu/main.c:48 > > > > > > > > > > > > > > > > -----Original Message----- > > > > From: Maxime Coquelin > > > > Sent: Thursday, January 12, 2023 5:26 PM > > > > To: Laurent Vivier > > > > Cc: qemu-devel@nongnu.org; Peter Maydell ; Yajun Wu ; Parav Pandit ; Michael S. Tsirkin > > > > Subject: Re: [PULL v4 76/83] vhost-user: Support vhost_dev_start > > > > > > > > External email: Use caution opening links or attachments > > > > > > > > > > > > Hi Laurent, > > > > > > > > On 1/11/23 10:50, Laurent Vivier wrote: > > > >> On 1/9/23 11:55, Michael S. Tsirkin wrote: > > > >>> On Fri, Jan 06, 2023 at 03:21:43PM +0100, Laurent Vivier wrote: > > > >>>> Hi, > > > >>>> > > > >>>> it seems this patch breaks vhost-user with DPDK. > > > >>>> > > > >>>> See > > > >>>> https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fbu > > > >>>> gzilla.redhat.com%2Fshow_bug.cgi%3Fid%3D2155173&data=05%7C01%7Cyajun > > > >>>> w%40nvidia.com%7C47e6e0fabd044383fd3308daf47f0253%7C43083d15727340c1 > > > >>>> b7db39efd9ccc17a%7C0%7C0%7C638091123577559319%7CUnknown%7CTWFpbGZsb3 > > > >>>> d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D > > > >>>> %7C3000%7C%7C%7C&sdata=1pjChYTKHVmBoempNitiZHBdrlPIMFjKoD6FeOVSay0%3 > > > >>>> D&reserved=0 > > > >>>> > > > >>>> it seems QEMU doesn't receive the expected commands sequence: > > > >>>> > > > >>>> Received unexpected msg type. Expected 22 received 40 Fail to update > > > >>>> device iotlb Received unexpected msg type. Expected 40 received 22 > > > >>>> Received unexpected msg type. Expected 22 received 11 Fail to update > > > >>>> device iotlb Received unexpected msg type. Expected 11 received 22 > > > >>>> vhost VQ 1 ring restore failed: -71: Protocol error (71) Received > > > >>>> unexpected msg type. Expected 22 received 11 Fail to update device > > > >>>> iotlb Received unexpected msg type. Expected 11 received 22 vhost VQ > > > >>>> 0 ring restore failed: -71: Protocol error (71) unable to start > > > >>>> vhost net: 71: falling back on userspace virtio > > > >>>> > > > >>>> It receives VHOST_USER_GET_STATUS (40) when it expects > > > >>>> VHOST_USER_IOTLB_MSG (22) and VHOST_USER_IOTLB_MSG when it expects > > > >>>> VHOST_USER_GET_STATUS. > > > >>>> and VHOST_USER_GET_VRING_BASE (11) when it expect > > > >>>> VHOST_USER_GET_STATUS and so on. > > > >>>> > > > >>>> Any idea? > > > > > > > > We only have a single thread on DPDK side to handle Vhost-user requests, it will read a request, handle it and reply to it. Then it reads the next one, etc... So I don't think it is possible to mix request replies order on DPDK side. > > > > > > > > Maybe there are two threads concurrently sending requests on QEMU side? > > > > > > > > Regards, > > > > Maxime > > > > > > > >>>> Thanks, > > > >>>> Laurent > > > >>> > > > >>> > > > >>> So I am guessing it's coming from: > > > >>> > > > >>> if (msg.hdr.request != request) { > > > >>> error_report("Received unexpected msg type. Expected %d > > > >>> received %d", > > > >>> request, msg.hdr.request); > > > >>> return -EPROTO; > > > >>> } > > > >>> > > > >>> in process_message_reply and/or in vhost_user_get_u64. > > > >>> > > > >>> > > > >>>> On 11/7/22 23:53, Michael S. Tsirkin wrote: > > > >>>>> From: Yajun Wu > > > >>>>> > > > >>>>> The motivation of adding vhost-user vhost_dev_start support is to > > > >>>>> improve backend configuration speed and reduce live migration VM > > > >>>>> downtime. > > > >>>>> > > > >>>>> Today VQ configuration is issued one by one. For virtio net with > > > >>>>> multi-queue support, backend needs to update RSS (Receive side > > > >>>>> scaling) on every rx queue enable. Updating RSS is time-consuming > > > >>>>> (typical time like 7ms). > > > >>>>> > > > >>>>> Implement already defined vhost status and message in the vhost > > > >>>>> specification [1]. > > > >>>>> (a) VHOST_USER_PROTOCOL_F_STATUS > > > >>>>> (b) VHOST_USER_SET_STATUS > > > >>>>> (c) VHOST_USER_GET_STATUS > > > >>>>> > > > >>>>> Send message VHOST_USER_SET_STATUS with VIRTIO_CONFIG_S_DRIVER_OK > > > >>>>> for device start and reset(0) for device stop. > > > >>>>> > > > >>>>> On reception of the DRIVER_OK message, backend can apply the needed > > > >>>>> setting only once (instead of incremental) and also utilize > > > >>>>> parallelism on enabling queues. > > > >>>>> > > > >>>>> This improves QEMU's live migration downtime with vhost user > > > >>>>> backend implementation by great margin, specially for the large > > > >>>>> number of VQs of 64 from 800 msec to 250 msec. > > > >>>>> > > > >>>>> [1] > > > >>>>> https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fq > > > >>>>> emu-project.gitlab.io%2Fqemu%2Finterop%2Fvhost-user.html&data=05%7C > > > >>>>> 01%7Cyajunw%40nvidia.com%7C47e6e0fabd044383fd3308daf47f0253%7C43083 > > > >>>>> d15727340c1b7db39efd9ccc17a%7C0%7C0%7C638091123577559319%7CUnknown% > > > >>>>> 7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiL > > > >>>>> CJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=YPbrFRJA92KLLwADMUDvwBt%2Fme2Ef > > > >>>>> GZuVANOmXH5pic%3D&reserved=0 > > > >>>>> > > > >>>>> Signed-off-by: Yajun Wu > > > >>>>> Acked-by: Parav Pandit > > > >>>>> Message-Id: <20221017064452.1226514-3-yajunw@nvidia.com> > > > >>>>> Reviewed-by: Michael S. Tsirkin > > > >>>>> Signed-off-by: Michael S. Tsirkin > > > >>> > > > >>> Probably easiest to debug from dpdk side. > > > >>> Does the problem go away if you disable the feature > > > >>> VHOST_USER_PROTOCOL_F_STATUS in dpdk? > > > >> > > > >> Maxime could you help to debug this? > > > >> > > > >> Thanks, > > > >> Laurent > > > >> > > > > > > > > > > > > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK