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 [off-list ref] wrote:

On Tue, Mar 14, 2023 at 11:48:33AM +0800, Jason Wang wrote:

quoted

On Thu, Mar 2, 2023 at 7:34 PM Stefano Garzarella [off-list ref] wrote:

quoted

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:
    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