better @subj: try late vq enable only if negotiated
On Tue, Feb 06, 2024 at 03:51:54PM +0100, Stefano Garzarella wrote:
> 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
