If VHOST_BACKEND_F_ENABLE_AFTER_DRIVER_OK is not negotiated, we expect the driver to enable virtqueue before setting DRIVER_OK. If the driver tries anyway, better to fail right away as soon as we get the ioctl. Let's also update the documentation to make it clearer.
We had a problem in QEMU for not meeting this requirement, see https://lore.kernel.org/qemu-devel/20240202132521.32714-1-kw...@redhat.com/ Fixes: 9f09fd6171fe ("vdpa: accept VHOST_BACKEND_F_ENABLE_AFTER_DRIVER_OK backend feature") Cc: epere...@redhat.com Signed-off-by: Stefano Garzarella <sgarz...@redhat.com> --- include/uapi/linux/vhost_types.h | 3 ++- drivers/vhost/vdpa.c | 4 ++++ 2 files changed, 6 insertions(+), 1 deletion(-) diff --git a/include/uapi/linux/vhost_types.h b/include/uapi/linux/vhost_types.h index d7656908f730..5df49b6021a7 100644 --- a/include/uapi/linux/vhost_types.h +++ b/include/uapi/linux/vhost_types.h @@ -182,7 +182,8 @@ struct vhost_vdpa_iova_range { /* Device can be resumed */ #define VHOST_BACKEND_F_RESUME 0x5 /* Device supports the driver enabling virtqueues both before and after - * DRIVER_OK + * DRIVER_OK. If this feature is not negotiated, the virtqueues must be + * enabled before setting DRIVER_OK. */ #define VHOST_BACKEND_F_ENABLE_AFTER_DRIVER_OK 0x6 /* Device may expose the virtqueue's descriptor area, driver area and diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c index bc4a51e4638b..1fba305ba8c1 100644 --- a/drivers/vhost/vdpa.c +++ b/drivers/vhost/vdpa.c @@ -651,6 +651,10 @@ static long vhost_vdpa_vring_ioctl(struct vhost_vdpa *v, unsigned int cmd, case VHOST_VDPA_SET_VRING_ENABLE: if (copy_from_user(&s, argp, sizeof(s))) return -EFAULT; + if (!vhost_backend_has_feature(vq, + VHOST_BACKEND_F_ENABLE_AFTER_DRIVER_OK) && + (ops->get_status(vdpa) & VIRTIO_CONFIG_S_DRIVER_OK)) + return -EINVAL; ops->set_vq_ready(vdpa, idx, s.num); return 0; case VHOST_VDPA_GET_VRING_GROUP: -- 2.43.0
