From c554f8768a18ceba173aedbd582c1cae43a41e2c Mon Sep 17 00:00:00 2001 From: Thomas Huth Date: Tue, 18 Jun 2024 14:19:58 +0200 Subject: [PATCH 1/2] hw/virtio: Fix the de-initialization of vhost-user devices MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit RH-Author: Thomas Huth RH-MergeRequest: 255: hw/virtio: Fix the de-initialization of vhost-user devices RH-Jira: RHEL-40708 RH-Acked-by: Cédric Le Goater RH-Acked-by: Miroslav Rezanina RH-Commit: [1/1] c7815a249ec135993f45934cab1c1f2c038b80ea (thuth/qemu-kvm-cs9) JIRA: https://issues.redhat.com/browse/RHEL-40708 The unrealize functions of the various vhost-user devices are calling the corresponding vhost_*_set_status() functions with a status of 0 to shut down the device correctly. Now these vhost_*_set_status() functions all follow this scheme: bool should_start = virtio_device_should_start(vdev, status); if (vhost_dev_is_started(&vvc->vhost_dev) == should_start) { return; } if (should_start) { /* ... do the initialization stuff ... */ } else { /* ... do the cleanup stuff ... */ } The problem here is virtio_device_should_start(vdev, 0) currently always returns "true" since it internally only looks at vdev->started instead of looking at the "status" parameter. Thus once the device got started once, virtio_device_should_start() always returns true and thus the vhost_*_set_status() functions return early, without ever doing any clean-up when being called with status == 0. This causes e.g. problems when trying to hot-plug and hot-unplug a vhost user devices multiple times since the de-initialization step is completely skipped during the unplug operation. This bug has been introduced in commit 9f6bcfd99f ("hw/virtio: move vm_running check to virtio_device_started") which replaced should_start = status & VIRTIO_CONFIG_S_DRIVER_OK; with should_start = virtio_device_started(vdev, status); which later got replaced by virtio_device_should_start(). This blocked the possibility to set should_start to false in case the status flag VIRTIO_CONFIG_S_DRIVER_OK was not set. Fix it by adjusting the virtio_device_should_start() function to only consider the status flag instead of vdev->started. Since this function is only used in the various vhost_*_set_status() functions for exactly the same purpose, it should be fine to fix it in this central place there without any risk to change the behavior of other code. Fixes: 9f6bcfd99f ("hw/virtio: move vm_running check to virtio_device_started") Buglink: https://issues.redhat.com/browse/RHEL-40708 Signed-off-by: Thomas Huth Message-Id: <20240618121958.88673-1-thuth@redhat.com> Reviewed-by: Manos Pitsidianakis Reviewed-by: Michael S. Tsirkin Signed-off-by: Michael S. Tsirkin (cherry picked from commit d72479b11797c28893e1e3fc565497a9cae5ca16) Signed-off-by: Thomas Huth --- include/hw/virtio/virtio.h | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h index 7d5ffdc145..2eafad17b8 100644 --- a/include/hw/virtio/virtio.h +++ b/include/hw/virtio/virtio.h @@ -470,9 +470,9 @@ static inline bool virtio_device_started(VirtIODevice *vdev, uint8_t status) * @vdev - the VirtIO device * @status - the devices status bits * - * This is similar to virtio_device_started() but also encapsulates a - * check on the VM status which would prevent a device starting - * anyway. + * This is similar to virtio_device_started() but ignores vdev->started + * and also encapsulates a check on the VM status which would prevent a + * device from starting anyway. */ static inline bool virtio_device_should_start(VirtIODevice *vdev, uint8_t status) { @@ -480,7 +480,7 @@ static inline bool virtio_device_should_start(VirtIODevice *vdev, uint8_t status return false; } - return virtio_device_started(vdev, status); + return status & VIRTIO_CONFIG_S_DRIVER_OK; } static inline void virtio_set_started(VirtIODevice *vdev, bool started) -- 2.39.3