From c9b51d54530c526f14ca0f3b9fc0bfa0b60d45ee Mon Sep 17 00:00:00 2001 From: Si-Wei Liu Date: Fri, 6 May 2022 19:28:18 -0700 Subject: [PATCH 20/24] virtio-net: don't handle mq request in userspace handler for vhost-vdpa MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit RH-Author: Jason Wang RH-MergeRequest: 187: Multiqueue fixes for vhost-vDPA RH-Commit: [7/7] 0e6684d12e42752deae8f5ebc56456fed174e0ed RH-Bugzilla: 2069946 RH-Acked-by: Eugenio Pérez RH-Acked-by: Cindy Lu RH-Acked-by: Laurent Vivier virtio_queue_host_notifier_read() tends to read pending event left behind on ioeventfd in the vhost_net_stop() path, and attempts to handle outstanding kicks from userspace vq handler. However, in the ctrl_vq handler, virtio_net_handle_mq() has a recursive call into virtio_net_set_status(), which may lead to segmentation fault as shown in below stack trace: 0 0x000055f800df1780 in qdev_get_parent_bus (dev=0x0) at ../hw/core/qdev.c:376 1 0x000055f800c68ad8 in virtio_bus_device_iommu_enabled (vdev=vdev@entry=0x0) at ../hw/virtio/virtio-bus.c:331 2 0x000055f800d70d7f in vhost_memory_unmap (dev=) at ../hw/virtio/vhost.c:318 3 0x000055f800d70d7f in vhost_memory_unmap (dev=, buffer=0x7fc19bec5240, len=2052, is_write=1, access_len=2052) at ../hw/virtio/vhost.c:336 4 0x000055f800d71867 in vhost_virtqueue_stop (dev=dev@entry=0x55f8037ccc30, vdev=vdev@entry=0x55f8044ec590, vq=0x55f8037cceb0, idx=0) at ../hw/virtio/vhost.c:1241 5 0x000055f800d7406c in vhost_dev_stop (hdev=hdev@entry=0x55f8037ccc30, vdev=vdev@entry=0x55f8044ec590) at ../hw/virtio/vhost.c:1839 6 0x000055f800bf00a7 in vhost_net_stop_one (net=0x55f8037ccc30, dev=0x55f8044ec590) at ../hw/net/vhost_net.c:315 7 0x000055f800bf0678 in vhost_net_stop (dev=dev@entry=0x55f8044ec590, ncs=0x55f80452bae0, data_queue_pairs=data_queue_pairs@entry=7, cvq=cvq@entry=1) at ../hw/net/vhost_net.c:423 8 0x000055f800d4e628 in virtio_net_set_status (status=, n=0x55f8044ec590) at ../hw/net/virtio-net.c:296 9 0x000055f800d4e628 in virtio_net_set_status (vdev=vdev@entry=0x55f8044ec590, status=15 '\017') at ../hw/net/virtio-net.c:370 10 0x000055f800d534d8 in virtio_net_handle_ctrl (iov_cnt=, iov=, cmd=0 '\000', n=0x55f8044ec590) at ../hw/net/virtio-net.c:1408 11 0x000055f800d534d8 in virtio_net_handle_ctrl (vdev=0x55f8044ec590, vq=0x7fc1a7e888d0) at ../hw/net/virtio-net.c:1452 12 0x000055f800d69f37 in virtio_queue_host_notifier_read (vq=0x7fc1a7e888d0) at ../hw/virtio/virtio.c:2331 13 0x000055f800d69f37 in virtio_queue_host_notifier_read (n=n@entry=0x7fc1a7e8894c) at ../hw/virtio/virtio.c:3575 14 0x000055f800c688e6 in virtio_bus_cleanup_host_notifier (bus=, n=n@entry=14) at ../hw/virtio/virtio-bus.c:312 15 0x000055f800d73106 in vhost_dev_disable_notifiers (hdev=hdev@entry=0x55f8035b51b0, vdev=vdev@entry=0x55f8044ec590) at ../../../include/hw/virtio/virtio-bus.h:35 16 0x000055f800bf00b2 in vhost_net_stop_one (net=0x55f8035b51b0, dev=0x55f8044ec590) at ../hw/net/vhost_net.c:316 17 0x000055f800bf0678 in vhost_net_stop (dev=dev@entry=0x55f8044ec590, ncs=0x55f80452bae0, data_queue_pairs=data_queue_pairs@entry=7, cvq=cvq@entry=1) at ../hw/net/vhost_net.c:423 18 0x000055f800d4e628 in virtio_net_set_status (status=, n=0x55f8044ec590) at ../hw/net/virtio-net.c:296 19 0x000055f800d4e628 in virtio_net_set_status (vdev=0x55f8044ec590, status=15 '\017') at ../hw/net/virtio-net.c:370 20 0x000055f800d6c4b2 in virtio_set_status (vdev=0x55f8044ec590, val=) at ../hw/virtio/virtio.c:1945 21 0x000055f800d11d9d in vm_state_notify (running=running@entry=false, state=state@entry=RUN_STATE_SHUTDOWN) at ../softmmu/runstate.c:333 22 0x000055f800d04e7a in do_vm_stop (state=state@entry=RUN_STATE_SHUTDOWN, send_stop=send_stop@entry=false) at ../softmmu/cpus.c:262 23 0x000055f800d04e99 in vm_shutdown () at ../softmmu/cpus.c:280 24 0x000055f800d126af in qemu_cleanup () at ../softmmu/runstate.c:812 25 0x000055f800ad5b13 in main (argc=, argv=, envp=) at ../softmmu/main.c:51 For now, temporarily disable handling MQ request from the ctrl_vq userspace hanlder to avoid the recursive virtio_net_set_status() call. Some rework is needed to allow changing the number of queues without going through a full virtio_net_set_status cycle, particularly for vhost-vdpa backend. This patch will need to be reverted as soon as future patches of having the change of #queues handled in userspace is merged. Fixes: 402378407db ("vhost-vdpa: multiqueue support") Signed-off-by: Si-Wei Liu Acked-by: Jason Wang Message-Id: <1651890498-24478-8-git-send-email-si-wei.liu@oracle.com> Reviewed-by: Michael S. Tsirkin Signed-off-by: Michael S. Tsirkin (cherry picked from commit 2a7888cc3aa31faee839fa5dddad354ff8941f4c) Signed-off-by: Jason Wang --- hw/net/virtio-net.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c index f118379bb4..7e172ef829 100644 --- a/hw/net/virtio-net.c +++ b/hw/net/virtio-net.c @@ -1373,6 +1373,7 @@ static int virtio_net_handle_mq(VirtIONet *n, uint8_t cmd, { VirtIODevice *vdev = VIRTIO_DEVICE(n); uint16_t queue_pairs; + NetClientState *nc = qemu_get_queue(n->nic); virtio_net_disable_rss(n); if (cmd == VIRTIO_NET_CTRL_MQ_HASH_CONFIG) { @@ -1404,6 +1405,18 @@ static int virtio_net_handle_mq(VirtIONet *n, uint8_t cmd, return VIRTIO_NET_ERR; } + /* Avoid changing the number of queue_pairs for vdpa device in + * userspace handler. A future fix is needed to handle the mq + * change in userspace handler with vhost-vdpa. Let's disable + * the mq handling from userspace for now and only allow get + * done through the kernel. Ripples may be seen when falling + * back to userspace, but without doing it qemu process would + * crash on a recursive entry to virtio_net_set_status(). + */ + if (nc->peer && nc->peer->info->type == NET_CLIENT_DRIVER_VHOST_VDPA) { + return VIRTIO_NET_ERR; + } + n->curr_queue_pairs = queue_pairs; /* stop the backend before changing the number of queue_pairs to avoid handling a * disabled queue */ -- 2.35.3