vhost-vdpa: introduce SUSPEND backend feature bit

Userland knows if it can suspend the device or not by checking this feature
bit.

It's only offered if the vdpa driver backend implements the suspend()
operation callback, and to offer it or userland to ack it if the backend
does not offer that callback is an error.

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
Message-Id: <20220810171512.2343333-3-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 2c997d77d2663871ae28056a959af791a41a610b..092752fea8e1d61f557f9ad72672a65978cb64af 100644 (file)
--- a/drivers/vhost/vdpa.c
+++ b/drivers/vhost/vdpa.c
@@ -347,6 +347,14 @@ static long vhost_vdpa_set_config(struct vhost_vdpa *v,
        return 0;
 }
 
+static bool vhost_vdpa_can_suspend(const struct vhost_vdpa *v)
+{
+       struct vdpa_device *vdpa = v->vdpa;
+       const struct vdpa_config_ops *ops = vdpa->config;
+
+       return ops->suspend;
+}
+
 static long vhost_vdpa_get_features(struct vhost_vdpa *v, u64 __user *featurep)
 {
        struct vdpa_device *vdpa = v->vdpa;
@@ -577,7 +585,11 @@ static long vhost_vdpa_unlocked_ioctl(struct file *filep,
        if (cmd == VHOST_SET_BACKEND_FEATURES) {
                if (copy_from_user(&features, featurep, sizeof(features)))
                        return -EFAULT;
-               if (features & ~VHOST_VDPA_BACKEND_FEATURES)
+               if (features & ~(VHOST_VDPA_BACKEND_FEATURES |
+                                BIT_ULL(VHOST_BACKEND_F_SUSPEND)))
+                       return -EOPNOTSUPP;
+               if ((features & BIT_ULL(VHOST_BACKEND_F_SUSPEND)) &&
+                    !vhost_vdpa_can_suspend(v))
                        return -EOPNOTSUPP;
                vhost_set_backend_features(&v->vdev, features);
                return 0;
@@ -628,6 +640,8 @@ static long vhost_vdpa_unlocked_ioctl(struct file *filep,
                break;
        case VHOST_GET_BACKEND_FEATURES:
                features = VHOST_VDPA_BACKEND_FEATURES;
+               if (vhost_vdpa_can_suspend(v))
+                       features |= BIT_ULL(VHOST_BACKEND_F_SUSPEND);
                if (copy_to_user(featurep, &features, sizeof(features)))
                        r = -EFAULT;
                break;

diff --git a/include/uapi/linux/vhost_types.h b/include/uapi/linux/vhost_types.h
index 634cee485abbcfbf186917892f8af4ab32a6822d..1bdd6e363f4c9f1557608bf2218363e7024b1489 100644 (file)
--- a/include/uapi/linux/vhost_types.h
+++ b/include/uapi/linux/vhost_types.h
@@ -161,5 +161,7 @@ struct vhost_vdpa_iova_range {
  * message
  */
 #define VHOST_BACKEND_F_IOTLB_ASID  0x3
+/* Device can be suspended */
+#define VHOST_BACKEND_F_SUSPEND  0x4
 
 #endif