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([2a01:e0a:e10:ef90:4c84:58cb:a1ef:8b78]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-431182d7c56sm123148555e9.7.2024.10.14.08.16.43 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 14 Oct 2024 08:16:43 -0700 (PDT) Message-ID: <14bcc2cf-f934-4aa3-8cab-21803a930adc@redhat.com> Date: Mon, 14 Oct 2024 17:16:43 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PULL 08/20] virtio-net: Add only one queue pair when realizing From: Laurent Vivier To: Akihiko Odaki Cc: Jason Wang , qemu-devel@nongnu.org References: <20240604073755.1859-1-jasowang@redhat.com> <20240604073755.1859-9-jasowang@redhat.com> Content-Language: en-US Autocrypt: addr=lvivier@redhat.com; keydata= xsFNBFYFJhkBEAC2me7w2+RizYOKZM+vZCx69GTewOwqzHrrHSG07MUAxJ6AY29/+HYf6EY2 WoeuLWDmXE7A3oJoIsRecD6BXHTb0OYS20lS608anr3B0xn5g0BX7es9Mw+hV/pL+63EOCVm SUVTEQwbGQN62guOKnJJJfphbbv82glIC/Ei4Ky8BwZkUuXd7d5NFJKC9/GDrbWdj75cDNQx UZ9XXbXEKY9MHX83Uy7JFoiFDMOVHn55HnncflUncO0zDzY7CxFeQFwYRbsCXOUL9yBtqLer Ky8/yjBskIlNrp0uQSt9LMoMsdSjYLYhvk1StsNPg74+s4u0Q6z45+l8RAsgLw5OLtTa+ePM JyS7OIGNYxAX6eZk1+91a6tnqfyPcMbduxyBaYXn94HUG162BeuyBkbNoIDkB7pCByed1A7q q9/FbuTDwgVGVLYthYSfTtN0Y60OgNkWCMtFwKxRaXt1WFA5ceqinN/XkgA+vf2Ch72zBkJL RBIhfOPFv5f2Hkkj0MvsUXpOWaOjatiu0fpPo6Hw14UEpywke1zN4NKubApQOlNKZZC4hu6/ 8pv2t4HRi7s0K88jQYBRPObjrN5+owtI51xMaYzvPitHQ2053LmgsOdN9EKOqZeHAYG2SmRW LOxYWKX14YkZI5j/TXfKlTpwSMvXho+efN4kgFvFmP6WT+tPnwARAQABzSNMYXVyZW50IFZp dmllciA8bHZpdmllckByZWRoYXQuY29tPsLBeAQTAQIAIgUCVgVQgAIbAwYLCQgHAwIGFQgC CQoLBBYCAwECHgECF4AACgkQ8ww4vT8vvjwpgg//fSGy0Rs/t8cPFuzoY1cex4limJQfReLr SJXCANg9NOWy/bFK5wunj+h/RCFxIFhZcyXveurkBwYikDPUrBoBRoOJY/BHK0iZo7/WQkur 6H5losVZtrotmKOGnP/lJYZ3H6OWvXzdz8LL5hb3TvGOP68K8Bn8UsIaZJoeiKhaNR0sOJyI YYbgFQPWMHfVwHD/U+/gqRhD7apVysxv5by/pKDln1I5v0cRRH6hd8M8oXgKhF2+rAOL7gvh jEHSSWKUlMjC7YwwjSZmUkL+TQyE18e2XBk85X8Da3FznrLiHZFHQ/NzETYxRjnOzD7/kOVy gKD/o7asyWQVU65mh/ECrtjfhtCBSYmIIVkopoLaVJ/kEbVJQegT2P6NgERC/31kmTF69vn8 uQyW11Hk8tyubicByL3/XVBrq4jZdJW3cePNJbTNaT0d/bjMg5zCWHbMErUib2Nellnbg6bc 2HLDe0NLVPuRZhHUHM9hO/JNnHfvgiRQDh6loNOUnm9Iw2YiVgZNnT4soUehMZ7au8PwSl4I KYE4ulJ8RRiydN7fES3IZWmOPlyskp1QMQBD/w16o+lEtY6HSFEzsK3o0vuBRBVp2WKnssVH qeeV01ZHw0bvWKjxVNOksP98eJfWLfV9l9e7s6TaAeySKRRubtJ+21PRuYAxKsaueBfUE7ZT 7zfOwU0EVgUmGQEQALxSQRbl/QOnmssVDxWhHM5TGxl7oLNJms2zmBpcmlrIsn8nNz0rRyxT 460k2niaTwowSRK8KWVDeAW6ZAaWiYjLlTunoKwvF8vP3JyWpBz0diTxL5o+xpvy/Q6YU3BN efdq8Vy3rFsxgW7mMSrI/CxJ667y8ot5DVugeS2NyHfmZlPGE0Nsy7hlebS4liisXOrN3jFz asKyUws3VXek4V65lHwB23BVzsnFMn/bw/rPliqXGcwl8CoJu8dSyrCcd1Ibs0/Inq9S9+t0 VmWiQWfQkz4rvEeTQkp/VfgZ6z98JRW7S6l6eophoWs0/ZyRfOm+QVSqRfFZdxdP2PlGeIFM C3fXJgygXJkFPyWkVElr76JTbtSHsGWbt6xUlYHKXWo+xf9WgtLeby3cfSkEchACrxDrQpj+ Jt/JFP+q997dybkyZ5IoHWuPkn7uZGBrKIHmBunTco1+cKSuRiSCYpBIXZMHCzPgVDjk4viP brV9NwRkmaOxVvye0vctJeWvJ6KA7NoAURplIGCqkCRwg0MmLrfoZnK/gRqVJ/f6adhU1oo6 z4p2/z3PemA0C0ANatgHgBb90cd16AUxpdEQmOCmdNnNJF/3Zt3inzF+NFzHoM5Vwq6rc1JP jfC3oqRLJzqAEHBDjQFlqNR3IFCIAo4SYQRBdAHBCzkM4rWyRhuVABEBAAHCwV8EGAECAAkF AlYFJhkCGwwACgkQ8ww4vT8vvjwg9w//VQrcnVg3TsjEybxDEUBm8dBmnKqcnTBFmxN5FFtI WlEuY8+YMiWRykd8Ln9RJ/98/ghABHz9TN8TRo2b6WimV64FmlVn17Ri6FgFU3xNt9TTEChq AcNg88eYryKsYpFwegGpwUlaUaaGh1m9OrTzcQy+klVfZWaVJ9Nw0keoGRGb8j4XjVpL8+2x OhXKrM1fzzb8JtAuSbuzZSQPDwQEI5CKKxp7zf76J21YeRrEW4WDznPyVcDTa+tz++q2S/Bp P4W98bXCBIuQgs2m+OflERv5c3Ojldp04/S4NEjXEYRWdiCxN7ca5iPml5gLtuvhJMSy36gl U6IW9kn30IWuSoBpTkgV7rLUEhh9Ms82VWW/h2TxL8enfx40PrfbDtWwqRID3WY8jLrjKfTd R3LW8BnUDNkG+c4FzvvGUs8AvuqxxyHbXAfDx9o/jXfPHVRmJVhSmd+hC3mcQ+4iX5bBPBPM oDqSoLt5w9GoQQ6gDVP2ZjTWqwSRMLzNr37rJjZ1pt0DCMMTbiYIUcrhX8eveCJtY7NGWNyx FCRkhxRuGcpwPmRVDwOl39MB3iTsRighiMnijkbLXiKoJ5CDVvX5yicNqYJPKh5MFXN1bvsB kmYiStMRbrD0HoY1kx5/VozBtc70OU0EB8Wrv9hZD+Ofp0T3KOr1RUHvCZoLURfFhSQ= In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=170.10.133.124; envelope-from=lvivier@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -21 X-Spam_score: -2.2 X-Spam_bar: -- X-Spam_report: (-2.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.076, 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_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=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 14/10/2024 10:30, Laurent Vivier wrote: > Hi Akihiko, > > On 04/06/2024 09:37, Jason Wang wrote: >> From: Akihiko Odaki >> >> Multiqueue usage is not negotiated yet when realizing. If more than >> one queue is added and the guest never requests to enable multiqueue, >> the extra queues will not be deleted when unrealizing and leak. >> >> Fixes: f9d6dbf0bf6e ("virtio-net: remove virtio queues if the guest doesn't support >> multiqueue") >> Signed-off-by: Akihiko Odaki >> Signed-off-by: Jason Wang >> --- >>   hw/net/virtio-net.c | 4 +--- >>   1 file changed, 1 insertion(+), 3 deletions(-) >> >> diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c >> index 3cee2ef3ac..a8db8bfd9c 100644 >> --- a/hw/net/virtio-net.c >> +++ b/hw/net/virtio-net.c >> @@ -3743,9 +3743,7 @@ static void virtio_net_device_realize(DeviceState *dev, Error **errp) >>       n->net_conf.tx_queue_size = MIN(virtio_net_max_tx_queue_size(n), >>                                       n->net_conf.tx_queue_size); >> -    for (i = 0; i < n->max_queue_pairs; i++) { >> -        virtio_net_add_queue(n, i); >> -    } >> +    virtio_net_add_queue(n, 0); >>       n->ctrl_vq = virtio_add_queue(vdev, 64, virtio_net_handle_ctrl); >>       qemu_macaddr_default_if_unset(&n->nic_conf.macaddr); > > This change breaks virtio net migration when multiqueue is enabled. > > I think this is because virtqueues are half initialized after migration : they are > initialized on guest side (kernel is using them) but not on QEMU side (realized has only > initialized one). After migration, they are not initialized by the call to > virtio_net_set_multiqueue() from virtio_net_set_features() because virtio_get_num_queues() > reports already n->max_queue_pairs as this value is coming from the source guest memory. > > I don't think we have a way to half-initialize a virtqueue (to initialize them only on > QEMU side as they are already initialized on kernel side). > > I think this change should be reverted to fix the migration issue. > Moreover, if I look in the code of virtio_load() and virtio_add_queue() we can guess it's not correct to migrate a virtqueue that is not initialized on the destination side because fields like 'vdev->vq[i].handle_output' or 'vdev->vq[i].used_elems' cannot be initialized by virtio_load() and neither by virtio_add_queue() after virtio_load() as fields like 'vring.num' are already initialized by virtio_load(). For instance, in virtio_load() we set: for (i = 0; i < num; i++) { vdev->vq[i].vring.num = qemu_get_be32(f); and in virtio_add_queue() we search for the firt available queue to add with: for (i = 0; i < VIRTIO_QUEUE_MAX; i++) { if (vdev->vq[i].vring.num == 0) break; } So virtio_add_queue() cannot be used to set: vdev->vq[i].handle_output = handle_output; vdev->vq[i].used_elems = g_new0(VirtQueueElement, queue_size); Moreover it would overwrite fields already set by virtio_load(): vdev->vq[i].vring.num = queue_size; vdev->vq[i].vring.align = VIRTIO_PCI_VRING_ALIGN; It also explains why virtio_net_change_num_queue_pairs() (indirectly called by virtio_net_set_features()) doesn't update the queue pair numbers: vring.num is already set so it thinks there is no more queues to add. Thanks, LAurent