Re: [PATCH v3 2/8] vhost-vdpa: use bind_mm/unbind_mm device callbacks

Jason Wang
2023-03-23T03:02:45Z

On Tue, Mar 21, 2023 at 11:42 PM Stefano Garzarella <sgarzare@redhat.com> wrote:
>
> When the user call VHOST_SET_OWNER ioctl and the vDPA device
> has `use_va` set to true, let's call the bind_mm callback.
> In this way we can bind the device to the user address space
> and directly use the user VA.
>
> The unbind_mm callback is called during the release after
> stopping the device.
>
> Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
> ---
>
> Notes:
> v3:
> - added `case VHOST_SET_OWNER` in vhost_vdpa_unlocked_ioctl() [Jason]
> v2:
> - call the new unbind_mm callback during the release [Jason]
> - avoid to call bind_mm callback after the reset, since the device
> is not detaching it now during the reset
>
> drivers/vhost/vdpa.c | 31 +++++++++++++++++++++++++++++++
> 1 file changed, 31 insertions(+)
>
> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
> index 7be9d9d8f01c..20250c3418b2 100644
> --- a/drivers/vhost/vdpa.c
> +++ b/drivers/vhost/vdpa.c
> @@ -219,6 +219,28 @@ static int vhost_vdpa_reset(struct vhost_vdpa *v)
> return vdpa_reset(vdpa);
> }
>
> +static long vhost_vdpa_bind_mm(struct vhost_vdpa *v)
> +{
> + struct vdpa_device *vdpa = v->vdpa;
> + const struct vdpa_config_ops *ops = vdpa->config;
> +
> + if (!vdpa->use_va || !ops->bind_mm)
> + return 0;
> +
> + return ops->bind_mm(vdpa, v->vdev.mm);
> +}
> +
> +static void vhost_vdpa_unbind_mm(struct vhost_vdpa *v)
> +{
> + struct vdpa_device *vdpa = v->vdpa;
> + const struct vdpa_config_ops *ops = vdpa->config;
> +
> + if (!vdpa->use_va || !ops->unbind_mm)
> + return;
> +
> + ops->unbind_mm(vdpa);
> +}
> +
> static long vhost_vdpa_get_device_id(struct vhost_vdpa *v, u8 __user *argp)
> {
> struct vdpa_device *vdpa = v->vdpa;
> @@ -709,6 +731,14 @@ static long vhost_vdpa_unlocked_ioctl(struct file *filep,
> case VHOST_VDPA_RESUME:
> r = vhost_vdpa_resume(v);
> break;
> + case VHOST_SET_OWNER:
> + r = vhost_dev_set_owner(d);

Nit:

I'd stick to the current way of passing the cmd, argp to
vhost_dev_ioctl() and introduce a new switch after the
vhost_dev_ioctl().

In this way, we are immune to any possible changes of dealing with
VHOST_SET_OWNER in vhost core.

Others look good.

Thanks

> + if (r)
> + break;
> + r = vhost_vdpa_bind_mm(v);
> + if (r)
> + vhost_dev_reset_owner(d, NULL);
> + break;
> default:
> r = vhost_dev_ioctl(&v->vdev, cmd, argp);
> if (r == -ENOIOCTLCMD)
> @@ -1287,6 +1317,7 @@ static int vhost_vdpa_release(struct inode *inode, struct file *filep)
> vhost_vdpa_clean_irq(v);
> vhost_vdpa_reset(v);
> vhost_dev_stop(&v->vdev);
> + vhost_vdpa_unbind_mm(v);
> vhost_vdpa_config_put(v);
> vhost_vdpa_cleanup(v);
> mutex_unlock(&d->mutex);
> --
> 2.39.2
>