On Mon, Jun 29, 2020 at 12:27:58PM +0200, Cornelia Huck wrote: > virtio-fs devices are only specified for virtio-1, so it is unclear > how a legacy or transitional device should behave. > > Signed-off-by: Cornelia Huck <coh...@redhat.com> > --- > > Forcing off legacy now (after the virtio-fs device has already been > available) may have unintended consequences, therefore RFC. > > By default, a virtio-pci device uses 'AUTO' for disable_legacy, which > will resolve to different values based upon which bus the device has > been plugged. Therefore, forcing disable_legacy may result in the same > device or a quite different one. > > Even though pre-virtio-1 behaviour of virtio-fs devices is simply not > specified, toggling disable_legacy will have implications for the BAR > layout, IIRC, and therefore a guest might end up getting a different > device, even if it always used it with virtio-1 anyway. > > Not sure what the best way to solve this problem is. Adding a compat > property for disable_legacy=AUTO may be the right thing to do, but I'm > not quite clear if there are any further implications here.
Well I notice that this device is not migrateable. So I think that we can just switch it over and be done with it. > Whatever we do here, we should make sure that the ccw incarnation of > this device indeed forces virtio-1. I agree. I notice that the API virtio_pci_force_virtio_1 turned out to be too fragile. I propose that instead we have a whitelist of devices which can be legacy or transitional. Force rest to modern. > --- > hw/virtio/vhost-user-fs-pci.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/hw/virtio/vhost-user-fs-pci.c b/hw/virtio/vhost-user-fs-pci.c > index e11c889d82b3..244205edf765 100644 > --- a/hw/virtio/vhost-user-fs-pci.c > +++ b/hw/virtio/vhost-user-fs-pci.c > @@ -44,6 +44,7 @@ static void vhost_user_fs_pci_realize(VirtIOPCIProxy > *vpci_dev, Error **errp) > vpci_dev->nvectors = dev->vdev.conf.num_request_queues + 2; > } > > + virtio_pci_force_virtio_1(vpci_dev); > qdev_realize(vdev, BUS(&vpci_dev->bus), errp); > } > > -- > 2.25.4
