On Mon, Nov 04, 2024 at 09:51:24PM +0530, Sahil Siddiq wrote: > Linux commit v5.14-rc1~30^2~8 enabled the vp_vdpa driver to set the > vq state to the device's initial state. This works differently for > split and packed vqs. > > With shadow virtqueues enabled, vhost-vdpa sets the vring base using > the VHOST_SET_VRING_BASE ioctl. The payload (vhost_vring_state) > differs for split and packed vqs. The implementation in QEMU currently > uses the payload required for split vqs (i.e., the num field of > vhost_vring_state is set to 0). The kernel throws EOPNOTSUPP when this > payload is used with packed vqs. > > This patch sets the num field in the payload appropriately so vhost-vdpa > (with the vp_vdpa driver) can use packed svqs. > > Link: https://lists.nongnu.org/archive/html/qemu-devel/2024-10/msg05106.html > Link: https://lore.kernel.org/r/20210602021536.39525-4-jasow...@redhat.com > Signed-off-by: Sahil Siddiq <sahil...@proton.me>
Looks like a feature, not a bugfix to me, so I guess - next release? > --- > QEMU currently does not support packed vhost shadow virtqueues. I am > working on adding support for packed svqs [1]. The test environment > that I am using [2] requires vhost-vdpa to use the relevant payload > when setting vring base. > > [1] https://wiki.qemu.org/Internships/ProjectIdeas/PackedShadowVirtqueue > [2] > https://www.redhat.com/en/blog/hands-vdpa-what-do-you-do-when-you-aint-got-hardware-part-2 > > hw/virtio/vhost-vdpa.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c > index 3cdaa12ed5..5f81945109 100644 > --- a/hw/virtio/vhost-vdpa.c > +++ b/hw/virtio/vhost-vdpa.c > @@ -1230,6 +1230,10 @@ static bool vhost_vdpa_svq_setup(struct vhost_dev *dev, > }; > int r; > > + if (virtio_vdev_has_feature(dev->vdev, VIRTIO_F_RING_PACKED)) { > + s.num = 0x80008000; > + } > + > r = vhost_vdpa_set_dev_vring_base(dev, &s); > if (unlikely(r)) { > error_setg_errno(errp, -r, "Cannot set vring base"); > -- > 2.47.0
