From: Hanna Czenczek Date: Tue, 23 Jul 2024 16:39:40 +0000 (+0200) Subject: virtio: Always reset vhost devices X-Git-Tag: v9.2.0-rc0~92^2~16 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=2688e8df60f5a655dc34c5e38523e425556f8483;p=thirdparty%2Fqemu.git virtio: Always reset vhost devices Requiring `vhost_started` to be true for resetting vhost devices in `virtio_reset()` seems like the wrong condition: Most importantly, the preceding `virtio_set_status(vdev, 0)` call will (for vhost devices) end up in `vhost_dev_stop()` (through vhost devices' `.set_status` implementations), setting `vdev->vhost_started = false`. Therefore, the gated `vhost_reset_device()` call is unreachable. `vhost_started` is not documented, so it is hard to say what exactly it is supposed to mean, but judging from the fact that `vhost_dev_start()` sets it and `vhost_dev_stop()` clears it, it seems like it indicates whether there is a vhost back-end, and whether that back-end is currently running and processing virtio requests. Making a reset conditional on whether the vhost back-end is processing virtio requests seems wrong; in fact, it is probably better to reset it only when it is not currently processing requests, which is exactly the current order of operations in `virtio_reset()`: First, the back-end is stopped through `virtio_set_status(vdev, 0)`, then we want to send a reset. Therefore, we should drop the `vhost_started` condition, but in its stead we then have to verify that we can indeed send a reset to this vhost device, by not just checking `k->get_vhost != NULL` (introduced by commit 95e1019a4a9), but also that the vhost back-end is connected (`hdev = k->get_vhost(); hdev != NULL && hdev->vhost_ops != NULL`). Reviewed-by: Stefan Hajnoczi Reviewed-by: Michael S. Tsirkin Signed-off-by: Hanna Czenczek Message-Id: <20240723163941.48775-3-hreitz@redhat.com> Reviewed-by: Michael S. Tsirkin Signed-off-by: Michael S. Tsirkin --- diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c index 9e10cbc0587..42589adf2c9 100644 --- a/hw/virtio/virtio.c +++ b/hw/virtio/virtio.c @@ -2331,8 +2331,12 @@ void virtio_reset(void *opaque) vdev->device_endian = virtio_default_endian(); } - if (vdev->vhost_started && k->get_vhost) { - vhost_reset_device(k->get_vhost(vdev)); + if (k->get_vhost) { + struct vhost_dev *hdev = k->get_vhost(vdev); + /* Only reset when vhost back-end is connected */ + if (hdev && hdev->vhost_ops) { + vhost_reset_device(hdev); + } } if (k->reset) {