[PATCH v6 2/3] vhost/vsock: discard IOTLB when ACCESS_PLATFORM is cleared

Clear the device IOTLB when userspace clears VIRTIO_F_ACCESS_PLATFORM.
Otherwise descriptor translation can continue to use mappings installed
before the feature change.

The common helper invalidates cached vring access and applies the
transition even while a backend is attached. The backend remains attached,
but userspace must configure the vring addresses for the new address mode
after a successful live transition.

Fixes: e13a6915a03f ("vhost/vsock: add IOTLB API support")

Suggested-by: Michael S. Tsirkin <[email protected]>

Signed-off-by: Jia Jia <[email protected]>
---
 drivers/vhost/vsock.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
index 9aaab6bb8061..77a5a6775c86 100644
--- a/drivers/vhost/vsock.c
+++ b/drivers/vhost/vsock.c
@@ -854,6 +854,7 @@ static int vhost_vsock_set_cid(struct vhost_vsock *vsock, u64 guest_cid)
 static int vhost_vsock_set_features(struct vhost_vsock *vsock, u64 features)
 {
 	struct vhost_virtqueue *vq;
+	int ret = -EFAULT;
 	int i;
 
 	if (features & ~VHOST_VSOCK_FEATURES)
@@ -865,9 +866,12 @@ static int vhost_vsock_set_features(struct vhost_vsock *vsock, u64 features)
 		goto err;
 	}
 
-	if ((features & (1ULL << VIRTIO_F_ACCESS_PLATFORM))) {
-		if (vhost_init_device_iotlb(&vsock->dev))
+	if (features & (1ULL << VIRTIO_F_ACCESS_PLATFORM)) {
+		ret = vhost_init_device_iotlb(&vsock->dev);
+		if (ret)
 			goto err;
+	} else {
+		vhost_clear_device_iotlb(&vsock->dev);
 	}
 
 	vsock->seqpacket_allow = features & (1ULL << VIRTIO_VSOCK_F_SEQPACKET);
@@ -883,7 +887,7 @@ static int vhost_vsock_set_features(struct vhost_vsock *vsock, u64 features)
 
 err:
 	mutex_unlock(&vsock->dev.mutex);
-	return -EFAULT;
+	return ret;
 }
 
 static long vhost_vsock_dev_ioctl(struct file *f, unsigned int ioctl,