vdpa: add get_backend_features vdpa operation

This operation allow vdpa parent to expose its own backend feature bits.

Next patches introduce a feature not compatible with all parent drivers:
the ability to enable vq after driver_ok.  Each parent must declare if
it allows it or not.

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
Acked-by: Shannon Nelson <shannon.nelson@amd.com>
Message-Id: <20230609092127.170673-4-eperezma@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
index bb57343..78379ff 100644 (file)
--- a/drivers/vhost/vdpa.c
+++ b/drivers/vhost/vdpa.c
@@ -403,6 +403,17 @@ static long vhost_vdpa_get_features(struct vhost_vdpa *v, u64 __user *featurep)
        return 0;
 }
 
+static u64 vhost_vdpa_get_backend_features(const struct vhost_vdpa *v)
+{
+       struct vdpa_device *vdpa = v->vdpa;
+       const struct vdpa_config_ops *ops = vdpa->config;
+
+       if (!ops->get_backend_features)
+               return 0;
+       else
+               return ops->get_backend_features(vdpa);
+}
+
 static long vhost_vdpa_set_features(struct vhost_vdpa *v, u64 __user *featurep)
 {
        struct vdpa_device *vdpa = v->vdpa;
@@ -742,6 +753,7 @@ static long vhost_vdpa_unlocked_ioctl(struct file *filep,
                        features |= BIT_ULL(VHOST_BACKEND_F_SUSPEND);
                if (vhost_vdpa_can_resume(v))
                        features |= BIT_ULL(VHOST_BACKEND_F_RESUME);
+               features |= vhost_vdpa_get_backend_features(v);
                if (copy_to_user(featurep, &features, sizeof(features)))
                        r = -EFAULT;
                break;

diff --git a/include/linux/vdpa.h b/include/linux/vdpa.h
index db1b0ea..0e65202 100644 (file)
--- a/include/linux/vdpa.h
+++ b/include/linux/vdpa.h
@@ -208,6 +208,9 @@ struct vdpa_map_file {
  *                             @vdev: vdpa device
  *                             Returns the virtio features support by the
  *                             device
+ * @get_backend_features:      Get parent-specific backend features (optional)
+ *                             Returns the vdpa features supported by the
+ *                             device.
  * @set_driver_features:       Set virtio features supported by the driver
  *                             @vdev: vdpa device
  *                             @features: feature support by the driver
@@ -358,6 +361,7 @@ struct vdpa_config_ops {
        u32 (*get_vq_align)(struct vdpa_device *vdev);
        u32 (*get_vq_group)(struct vdpa_device *vdev, u16 idx);
        u64 (*get_device_features)(struct vdpa_device *vdev);
+       u64 (*get_backend_features)(const struct vdpa_device *vdev);
        int (*set_driver_features)(struct vdpa_device *vdev, u64 features);
        u64 (*get_driver_features)(struct vdpa_device *vdev);
        void (*set_config_cb)(struct vdpa_device *vdev,