[PATCH RFC v2 2/3] vhost-vdpa: introduce descriptor group backend feature

[Si-Wei Liu <si-wei.liu@oracle.com>]

Userspace knows if the device has dedicated descriptor group or not
by checking this feature bit.

It's only exposed if the vdpa driver backend implements the
.get_vq_desc_group() operation callback. Userspace trying to negotiate
this feature when it or the dependent _F_IOTLB_ASID feature hasn't
been exposed will result in an error.

Signed-off-by: Si-Wei Liu <si-wei.liu@oracle.com>
Acked-by: Eugenio Pérez <eperezma@redhat.com>

---
RFC v1 -> v2:
  - add clarifications for what areas F_DESC_ASID should cover
---
 drivers/vhost/vdpa.c             | 17 +++++++++++++++++
 include/uapi/linux/vhost_types.h |  5 +++++
 2 files changed, 22 insertions(+)

diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
index b43e868..f2e5dce 100644
--- a/drivers/vhost/vdpa.c
+++ b/drivers/vhost/vdpa.c
@@ -389,6 +389,14 @@ static bool vhost_vdpa_can_resume(const struct vhost_vdpa *v)
 	return ops->resume;
 }
 
+static bool vhost_vdpa_has_desc_group(const struct vhost_vdpa *v)
+{
+	struct vdpa_device *vdpa = v->vdpa;
+	const struct vdpa_config_ops *ops = vdpa->config;
+
+	return ops->get_vq_desc_group;
+}
+
 static long vhost_vdpa_get_features(struct vhost_vdpa *v, u64 __user *featurep)
 {
 	struct vdpa_device *vdpa = v->vdpa;
@@ -679,6 +687,7 @@ static long vhost_vdpa_unlocked_ioctl(struct file *filep,
 		if (copy_from_user(&features, featurep, sizeof(features)))
 			return -EFAULT;
 		if (features & ~(VHOST_VDPA_BACKEND_FEATURES |
+				 BIT_ULL(VHOST_BACKEND_F_DESC_ASID) |
 				 BIT_ULL(VHOST_BACKEND_F_SUSPEND) |
 				 BIT_ULL(VHOST_BACKEND_F_RESUME)))
 			return -EOPNOTSUPP;
@@ -688,6 +697,12 @@ static long vhost_vdpa_unlocked_ioctl(struct file *filep,
 		if ((features & BIT_ULL(VHOST_BACKEND_F_RESUME)) &&
 		     !vhost_vdpa_can_resume(v))
 			return -EOPNOTSUPP;
+		if ((features & BIT_ULL(VHOST_BACKEND_F_DESC_ASID)) &&
+		    !(features & BIT_ULL(VHOST_BACKEND_F_IOTLB_ASID)))
+			return -EINVAL;
+		if ((features & BIT_ULL(VHOST_BACKEND_F_DESC_ASID)) &&
+		     !vhost_vdpa_has_desc_group(v))
+			return -EOPNOTSUPP;
 		vhost_set_backend_features(&v->vdev, features);
 		return 0;
 	}
@@ -741,6 +756,8 @@ 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);
+		if (vhost_vdpa_has_desc_group(v))
+			features |= BIT_ULL(VHOST_BACKEND_F_DESC_ASID);
 		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 d3aad12a..6acc604 100644
--- a/include/uapi/linux/vhost_types.h
+++ b/include/uapi/linux/vhost_types.h
@@ -181,5 +181,10 @@ struct vhost_vdpa_iova_range {
 #define VHOST_BACKEND_F_SUSPEND  0x4
 /* Device can be resumed */
 #define VHOST_BACKEND_F_RESUME  0x5
+/* Device may expose the virtqueue's descriptor area, driver area and
+ * device area to a different group for ASID binding than where its
+ * buffers may reside. Requires VHOST_BACKEND_F_IOTLB_ASID.
+ */
+#define VHOST_BACKEND_F_DESC_ASID    0x6
 
 #endif
-- 
1.8.3.1

_______________________________________________
Virtualization mailing list
Virtualization@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/virtualization