[PATCH] vhost-vdpa: Expose ASID group change after DRIVER_OK via backend feature

[PATCH] vhost-vdpa: Expose ASID group change after DRIVER_OK via backend feature

[Dragos Tatulea]

The commit in the fixes tag blocked VHOST_VDPA_SET_GROUP_ASID operations
once DRIVER_OK is set. That is too strict for devices which can safely
handle this during live migration flows.

Bring back this behavior under a new vhost backend feature flag. The
feature is supported by mlx5 and vdpa_sim devices.

Fixes: 3543b04a4ea3 ("vhost: forbid change vq groups ASID if DRIVER_OK is set")
Signed-off-by: Dragos Tatulea <dtatulea@nvidia.com>
Reviewed-by: Shahar Shitrit <shshitrit@nvidia.com>
---
 drivers/vdpa/mlx5/net/mlx5_vnet.c |  3 ++-
 drivers/vdpa/vdpa_sim/vdpa_sim.c  |  3 ++-
 drivers/vhost/vdpa.c              | 13 +++++++++++--
 include/uapi/linux/vhost_types.h  |  4 ++++
 4 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c
index ad0d5fbbbca8..f89177957c76 100644
--- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
+++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
@@ -2906,7 +2906,8 @@ static void unregister_link_notifier(struct mlx5_vdpa_net *ndev)
 
 static u64 mlx5_vdpa_get_backend_features(const struct vdpa_device *vdpa)
 {
-	return BIT_ULL(VHOST_BACKEND_F_ENABLE_AFTER_DRIVER_OK);
+	return BIT_ULL(VHOST_BACKEND_F_ENABLE_AFTER_DRIVER_OK) |
+	       BIT_ULL(VHOST_BACKEND_F_GROUP_ASID_AFTER_DRIVER_OK);
 }
 
 static int mlx5_vdpa_set_driver_features(struct vdpa_device *vdev, u64 features)
diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.c b/drivers/vdpa/vdpa_sim/vdpa_sim.c
index 8cb1cc2ea139..253c7fb35ea0 100644
--- a/drivers/vdpa/vdpa_sim/vdpa_sim.c
+++ b/drivers/vdpa/vdpa_sim/vdpa_sim.c
@@ -428,7 +428,8 @@ static u64 vdpasim_get_device_features(struct vdpa_device *vdpa)
 
 static u64 vdpasim_get_backend_features(const struct vdpa_device *vdpa)
 {
-	return BIT_ULL(VHOST_BACKEND_F_ENABLE_AFTER_DRIVER_OK);
+	return BIT_ULL(VHOST_BACKEND_F_ENABLE_AFTER_DRIVER_OK) |
+	       BIT_ULL(VHOST_BACKEND_F_GROUP_ASID_AFTER_DRIVER_OK);
 }
 
 static int vdpasim_set_driver_features(struct vdpa_device *vdpa, u64 features)
diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
index 692564b1bcbb..67b3f49fa709 100644
--- a/drivers/vhost/vdpa.c
+++ b/drivers/vhost/vdpa.c
@@ -682,7 +682,8 @@ static long vhost_vdpa_vring_ioctl(struct vhost_vdpa *v, unsigned int cmd,
 			return -EFAULT;
 		if (idx >= vdpa->ngroups || s.num >= vdpa->nas)
 			return -EINVAL;
-		if (ops->get_status(vdpa) & VIRTIO_CONFIG_S_DRIVER_OK)
+		if ((ops->get_status(vdpa) & VIRTIO_CONFIG_S_DRIVER_OK) &&
+		    !vhost_backend_has_feature(vq, VHOST_BACKEND_F_GROUP_ASID_AFTER_DRIVER_OK))
 			return -EBUSY;
 		if (!ops->set_group_asid)
 			return -EOPNOTSUPP;
@@ -791,7 +792,8 @@ static long vhost_vdpa_unlocked_ioctl(struct file *filep,
 				 BIT_ULL(VHOST_BACKEND_F_IOTLB_PERSIST) |
 				 BIT_ULL(VHOST_BACKEND_F_SUSPEND) |
 				 BIT_ULL(VHOST_BACKEND_F_RESUME) |
-				 BIT_ULL(VHOST_BACKEND_F_ENABLE_AFTER_DRIVER_OK)))
+				 BIT_ULL(VHOST_BACKEND_F_ENABLE_AFTER_DRIVER_OK) |
+				 BIT_ULL(VHOST_BACKEND_F_GROUP_ASID_AFTER_DRIVER_OK)))
 			return -EOPNOTSUPP;
 		if ((features & BIT_ULL(VHOST_BACKEND_F_SUSPEND)) &&
 		     !vhost_vdpa_can_suspend(v))
@@ -805,6 +807,13 @@ static long vhost_vdpa_unlocked_ioctl(struct file *filep,
 		if ((features & BIT_ULL(VHOST_BACKEND_F_DESC_ASID)) &&
 		     !vhost_vdpa_has_desc_group(v))
 			return -EOPNOTSUPP;
+		if (features & BIT_ULL(VHOST_BACKEND_F_GROUP_ASID_AFTER_DRIVER_OK)) {
+			if (!(features & BIT_ULL(VHOST_BACKEND_F_IOTLB_ASID)))
+				return -EINVAL;
+			if (!(vhost_vdpa_get_backend_features(v) &
+				BIT_ULL(VHOST_BACKEND_F_GROUP_ASID_AFTER_DRIVER_OK)))
+				return -EOPNOTSUPP;
+		}
 		if ((features & BIT_ULL(VHOST_BACKEND_F_IOTLB_PERSIST)) &&
 		     !vhost_vdpa_has_persistent_map(v))
 			return -EOPNOTSUPP;
diff --git a/include/uapi/linux/vhost_types.h b/include/uapi/linux/vhost_types.h
index 1c39cc5f5a31..ec1ff8a2e260 100644
--- a/include/uapi/linux/vhost_types.h
+++ b/include/uapi/linux/vhost_types.h
@@ -197,5 +197,9 @@ struct vhost_vdpa_iova_range {
 #define VHOST_BACKEND_F_DESC_ASID    0x7
 /* IOTLB don't flush memory mapping across device reset */
 #define VHOST_BACKEND_F_IOTLB_PERSIST  0x8
+/* Device supports changing the group ASID after DRIVER_OK.
+ * Requires VHOST_BACKEND_F_IOTLB_ASID.
+ */
+#define VHOST_BACKEND_F_GROUP_ASID_AFTER_DRIVER_OK  0x9
 
 #endif
-- 
2.54.0