linux-kernel - Re: [PATCH v3 2/8] vhost-vdpa: use bind_mm/unbind

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Message-ID: <CACGkMEtq8PWL01WBL2Ve-Yr=ZO+su73tKuOh1EBLagkrLdiCaQ@mail.gmail.com>
Date:   Thu, 23 Mar 2023 11:01:39 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Stefano Garzarella <sgarzare@...hat.com>
Cc:     virtualization@...ts.linux-foundation.org, stefanha@...hat.com,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Andrey Zhadchenko <andrey.zhadchenko@...tuozzo.com>,
        eperezma@...hat.com, netdev@...r.kernel.org, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/8] vhost-vdpa: use bind_mm/unbind_mm device callbacks

On Tue, Mar 21, 2023 at 11:42 PM Stefano Garzarella <sgarzare@...hat.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@...hat.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
>