On Tue, Nov 22, 2022 at 07:01:38PM +0100, Eugenio Perez Martin wrote:
On Tue, Nov 22, 2022 at 4:13 AM Jason Wang <jasow...@redhat.com> wrote:On Mon, Nov 21, 2022 at 6:11 PM Stefano Garzarella <sgarz...@redhat.com> wrote: > > Commit 69e1c14aa2 ("virtio: core: vq reset feature negotation support") > enabled VIRTIO_F_RING_RESET by default for all virtio devices. > > This feature is not currently emulated by QEMU, so for vhost and > vhost-user devices we need to make sure it is supported by the offloaded > device emulation (in-kernel or in another process). > To do this we need to add VIRTIO_F_RING_RESET to the features bitmap > passed to vhost_get_features(). This way it will be masked if the device > does not support it. > > This issue was initially discovered with vhost-vsock and vhost-user-vsock, > and then also tested with vhost-user-rng which confirmed the same issue. > They fail when sending features through VHOST_SET_FEATURES ioctl or > VHOST_USER_SET_FEATURES message, since VIRTIO_F_RING_RESET is negotiated > by the guest (Linux >= v6.0), but not supported by the device. > > Fixes: 69e1c14aa2 ("virtio: core: vq reset feature negotation support") > Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1318 > Signed-off-by: Stefano Garzarella <sgarz...@redhat.com> Acked-by: Jason Wang <jasow...@redhat.com> > --- > > To prevent this problem in the future, perhaps we should provide a function > (e.g. vhost_device_get_features) where we go to mask all non-device-specific > features (e.g VIRTIO_F_*, VIRTIO_RING_F_*) that are not emulated by QEMU but > we expect them to be emulated by the vhost or vhost-user devices. Adding Eugenio, this might not be true if we want to use shadow virtqueue for emulating some features?I think we should be able to introduce that in the (hypothetical) vhost_device_get_features if SVQ starts emulating a ring feature, isn't it?
Yep, I think so. The idea is to have a single place where to do it.
I think a first version not aware of SVQ is fine anyway, and to introduce it later should be easy.
Thanks for the feedbacks, I'll keep you CCed. Thanks, Stefano
