On Wed, 10 Jul 2024 at 13:25, Hanna Czenczek <hre...@redhat.com> wrote: > > 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`). > > Signed-off-by: Hanna Czenczek <hre...@redhat.com>
I think an additional SET_STATUS 0 call is made to the vDPA vhost backend after this patch, but that seems fine. Reviewed-by: Stefan Hajnoczi <stefa...@redhat.com> > --- > 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 = 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) { > -- > 2.45.2 > >