On Mon, Jul 03, 2023 at 04:22:18PM +0200, Eugenio Pérez wrote:
> With the current code it is accepted as long as userland send it.
>
> Although userland should not set a feature flag that has not been
> offered to it with VHOST_GET_BACKEND_FEATURES, the current code will not
> complain for it.
>
> Since there is no specific reason for any parent to reject that backend
> feature bit when it has been proposed, let's control it at vdpa frontend
> level. Future patches may move this control to the parent driver.
>
> Fixes: 967800d2d52e ("vdpa: accept VHOST_BACKEND_F_ENABLE_AFTER_DRIVER_OK backend feature")
> Signed-off-by: Eugenio Pérez <eperezma@xxxxxxxxxx>
Please do send v3. And again, I don't want to send "after driver ok" hack
upstream at all, I merged it in next just to give it some testing.
We want RING_ACCESS_AFTER_KICK or some such.
> ---
> Sent with Fixes: tag pointing to git.kernel.org/pub/scm/linux/kernel/git/mst
> commit. Please let me know if I should send a v3 of [1] instead.
>
> [1] https://lore.kernel.org/lkml/20230609121244-mutt-send-email-mst@xxxxxxxxxx/T/
> ---
> drivers/vhost/vdpa.c | 7 +++++--
> 1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
> index e1abf29fed5b..a7e554352351 100644
> --- a/drivers/vhost/vdpa.c
> +++ b/drivers/vhost/vdpa.c
> @@ -681,18 +681,21 @@ static long vhost_vdpa_unlocked_ioctl(struct file *filep,
> {
> struct vhost_vdpa *v = filep->private_data;
> struct vhost_dev *d = &v->vdev;
> + const struct vdpa_config_ops *ops = v->vdpa->config;
> void __user *argp = (void __user *)arg;
> u64 __user *featurep = argp;
> - u64 features;
> + u64 features, parent_features = 0;
> long r = 0;
>
> if (cmd == VHOST_SET_BACKEND_FEATURES) {
> if (copy_from_user(&features, featurep, sizeof(features)))
> return -EFAULT;
> + if (ops->get_backend_features)
> + parent_features = ops->get_backend_features(v->vdpa);
> if (features & ~(VHOST_VDPA_BACKEND_FEATURES |
> BIT_ULL(VHOST_BACKEND_F_SUSPEND) |
> BIT_ULL(VHOST_BACKEND_F_RESUME) |
> - BIT_ULL(VHOST_BACKEND_F_ENABLE_AFTER_DRIVER_OK)))
> + parent_features))
> return -EOPNOTSUPP;
> if ((features & BIT_ULL(VHOST_BACKEND_F_SUSPEND)) &&
> !vhost_vdpa_can_suspend(v))
> --
> 2.39.3
