linux-kernel - Re: [PATCH v2 2/8] vhost-vdpa: use bind_mm/unbind

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Message-ID: <CAGxU2F6Pa9Dar0MVvW=qUh0k30pdtbrSy_5u2NuREd8u-id=MA@mail.gmail.com>
Date:   Thu, 16 Mar 2023 11:11:15 +0100
From:   Stefano Garzarella <sgarzare@...hat.com>
To:     Jason Wang <jasowang@...hat.com>
Cc:     virtualization@...ts.linux-foundation.org,
        Andrey Zhadchenko <andrey.zhadchenko@...tuozzo.com>,
        eperezma@...hat.com, netdev@...r.kernel.org, stefanha@...hat.com,
        linux-kernel@...r.kernel.org,
        "Michael S. Tsirkin" <mst@...hat.com>, kvm@...r.kernel.org
Subject: Re: [PATCH v2 2/8] vhost-vdpa: use bind_mm/unbind_mm device callbacks

On Thu, Mar 16, 2023 at 9:31 AM Stefano Garzarella <sgarzare@...hat.com> wrote:
>
> On Tue, Mar 14, 2023 at 11:48:33AM +0800, Jason Wang wrote:
> >On Thu, Mar 2, 2023 at 7:34 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:
> >>     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 | 30 ++++++++++++++++++++++++++++++
> >>  1 file changed, 30 insertions(+)
> >>
> >> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
> >> index dc12dbd5b43b..1ab89fccd825 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;
> >> @@ -711,6 +733,13 @@ static long vhost_vdpa_unlocked_ioctl(struct file *filep,
> >>                 break;
> >>         default:
> >>                 r = vhost_dev_ioctl(&v->vdev, cmd, argp);
> >> +               if (!r && cmd == VHOST_SET_OWNER) {
> >> +                       r = vhost_vdpa_bind_mm(v);
> >> +                       if (r) {
> >> +                               vhost_dev_reset_owner(&v->vdev, NULL);
> >> +                               break;
> >> +                       }
> >> +               }
> >
> >Nit: is it better to have a new condition/switch branch instead of
> >putting them under default? (as what vring_ioctl did).
>
> Yep, I agree!
>
> I'll change it.

Or maybe I can simply add `case VHOST_SET_OWNER` on this switch and call
vhost_dev_set_owner() and vhost_vdpa_bind_mm(), I mean something like
this:

diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
index 331d4a718bf6..20250c3418b2 100644
--- a/drivers/vhost/vdpa.c
+++ b/drivers/vhost/vdpa.c
@@ -731,15 +731,16 @@ 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);
+               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 && cmd == VHOST_SET_OWNER) {
-                       r = vhost_vdpa_bind_mm(v);
-                       if (r) {
-                               vhost_dev_reset_owner(&v->vdev, NULL);
-                               break;
-                       }
-               }
                if (r == -ENOIOCTLCMD)
                        r = vhost_vdpa_vring_ioctl(v, cmd, argp);
                break;

WDYT?

Thanks,
Stefano