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Tsirkin" Subject: [PATCH] virtio: Always reset vhost devices Date: Wed, 10 Jul 2024 13:23:10 +0200 Message-ID: <20240710112310.316551-1-hreitz@redhat.com> X-Mailer: git-send-email 2.45.2 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=170.10.129.124; envelope-from=hreitz@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=-0.144, 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_H4=0.001, RCVD_IN_MSPIKE_WL=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+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @redhat.com) X-ZM-MESSAGEID: 1720610697321116600 Content-Type: text/plain; charset="utf-8" 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 =3D 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 !=3D NULL` (introduced by commit 95e1019a4a9), but also that the vhost back-end is connected (`hdev =3D k->get_vhost(); hdev !=3D NULL && hdev->vhost_ops !=3D NULL`). Signed-off-by: Hanna Czenczek Reviewed-by: Stefan Hajnoczi --- hw/virtio/virtio.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c index 893a072c9d..4410d62126 100644 --- a/hw/virtio/virtio.c +++ b/hw/virtio/virtio.c @@ -2146,8 +2146,12 @@ void virtio_reset(void *opaque) vdev->device_endian =3D virtio_default_endian(); } =20 - if (vdev->vhost_started && k->get_vhost) { - vhost_reset_device(k->get_vhost(vdev)); + if (k->get_vhost) { + struct vhost_dev *hdev =3D k->get_vhost(vdev); + /* Only reset when vhost back-end is connected */ + if (hdev && hdev->vhost_ops) { + vhost_reset_device(hdev); + } } =20 if (k->reset) { --=20 2.45.2