vhost-vdpa: introduce descriptor group backend feature

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>
Acked-by: Jason Wang <jasowang@redhat.com>
Message-Id: <20231018171456.1624030-5-dtatulea@nvidia.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Si-Wei Liu <si-wei.liu@oracle.com>
Tested-by: Si-Wei Liu <si-wei.liu@oracle.com>
Tested-by: Lei Yang <leiyang@redhat.com>

diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
index 78379ffd23363d99cd4c95daf048d1955fc185f3..2f21798a37ee01ce505523a167e91ede72609f08 100644 (file)
--- 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;
@@ -690,6 +698,7 @@ 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) |
                                 BIT_ULL(VHOST_BACKEND_F_ENABLE_AFTER_DRIVER_OK)))
@@ -700,6 +709,12 @@ 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;
        }
@@ -753,6 +768,8 @@ 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);
                features |= vhost_vdpa_get_backend_features(v);
                if (copy_to_user(featurep, &features, sizeof(features)))
                        r = -EFAULT;

diff --git a/include/uapi/linux/vhost_types.h b/include/uapi/linux/vhost_types.h
index 2d827d22cd99d2e507acaebcb3d502ac15417770..18ad6ae7ab5c6ab1fa340256b00c0d7c73ba24bf 100644 (file)
--- a/include/uapi/linux/vhost_types.h
+++ b/include/uapi/linux/vhost_types.h
@@ -185,5 +185,10 @@ struct vhost_vdpa_iova_range {
  * DRIVER_OK
  */
 #define VHOST_BACKEND_F_ENABLE_AFTER_DRIVER_OK  0x6
+/* 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    0x7
 
 #endif