vhost: switch to use new message format
We use to have message like:
struct vhost_msg {
int type;
union {
struct vhost_iotlb_msg iotlb;
__u8 padding[64];
};
};
Unfortunately, there will be a hole of 32bit in 64bit machine because
of the alignment. This leads a different formats between 32bit API and
64bit API. What's more it will break 32bit program running on 64bit
machine.
So fixing this by introducing a new message type with an explicit
32bit reserved field after type like:
struct vhost_msg_v2 {
__u32 type;
__u32 reserved;
union {
struct vhost_iotlb_msg iotlb;
__u8 padding[64];
};
};
We will have a consistent ABI after switching to use this. To enable
this capability, introduce a new ioctl (VHOST_SET_BAKCEND_FEATURE) for
userspace to enable this feature (VHOST_BACKEND_F_IOTLB_V2).
Fixes: 6b1e6cc7855b ("vhost: new device IOTLB API")
Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index a502f1a..6f6c42d 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -315,6 +315,7 @@ static void vhost_vq_reset(struct vhost_dev *dev,
vq->log_addr = -1ull;
vq->private_data = NULL;
vq->acked_features = 0;
+ vq->acked_backend_features = 0;
vq->log_base = NULL;
vq->error_ctx = NULL;
vq->kick = NULL;
@@ -1027,28 +1028,40 @@ static int vhost_process_iotlb_msg(struct vhost_dev *dev,
ssize_t vhost_chr_write_iter(struct vhost_dev *dev,
struct iov_iter *from)
{
- struct vhost_msg_node node;
- unsigned size = sizeof(struct vhost_msg);
- size_t ret;
- int err;
+ struct vhost_iotlb_msg msg;
+ size_t offset;
+ int type, ret;
- if (iov_iter_count(from) < size)
- return 0;
- ret = copy_from_iter(&node.msg, size, from);
- if (ret != size)
+ ret = copy_from_iter(&type, sizeof(type), from);
+ if (ret != sizeof(type))
goto done;
- switch (node.msg.type) {
+ switch (type) {
case VHOST_IOTLB_MSG:
- err = vhost_process_iotlb_msg(dev, &node.msg.iotlb);
- if (err)
- ret = err;
+ /* There maybe a hole after type for V1 message type,
+ * so skip it here.
+ */
+ offset = offsetof(struct vhost_msg, iotlb) - sizeof(int);
+ break;
+ case VHOST_IOTLB_MSG_V2:
+ offset = sizeof(__u32);
break;
default:
ret = -EINVAL;
- break;
+ goto done;
}
+ iov_iter_advance(from, offset);
+ ret = copy_from_iter(&msg, sizeof(msg), from);
+ if (ret != sizeof(msg))
+ goto done;
+ if (vhost_process_iotlb_msg(dev, &msg)) {
+ ret = -EFAULT;
+ goto done;
+ }
+
+ ret = (type == VHOST_IOTLB_MSG) ? sizeof(struct vhost_msg) :
+ sizeof(struct vhost_msg_v2);
done:
return ret;
}
@@ -1107,13 +1120,28 @@ ssize_t vhost_chr_read_iter(struct vhost_dev *dev, struct iov_iter *to,
finish_wait(&dev->wait, &wait);
if (node) {
- ret = copy_to_iter(&node->msg, size, to);
+ struct vhost_iotlb_msg *msg;
+ void *start = &node->msg;
- if (ret != size || node->msg.type != VHOST_IOTLB_MISS) {
+ switch (node->msg.type) {
+ case VHOST_IOTLB_MSG:
+ size = sizeof(node->msg);
+ msg = &node->msg.iotlb;
+ break;
+ case VHOST_IOTLB_MSG_V2:
+ size = sizeof(node->msg_v2);
+ msg = &node->msg_v2.iotlb;
+ break;
+ default:
+ BUG();
+ break;
+ }
+
+ ret = copy_to_iter(start, size, to);
+ if (ret != size || msg->type != VHOST_IOTLB_MISS) {
kfree(node);
return ret;
}
-
vhost_enqueue_msg(dev, &dev->pending_list, node);
}
@@ -1126,12 +1154,19 @@ static int vhost_iotlb_miss(struct vhost_virtqueue *vq, u64 iova, int access)
struct vhost_dev *dev = vq->dev;
struct vhost_msg_node *node;
struct vhost_iotlb_msg *msg;
+ bool v2 = vhost_backend_has_feature(vq, VHOST_BACKEND_F_IOTLB_MSG_V2);
- node = vhost_new_msg(vq, VHOST_IOTLB_MISS);
+ node = vhost_new_msg(vq, v2 ? VHOST_IOTLB_MSG_V2 : VHOST_IOTLB_MSG);
if (!node)
return -ENOMEM;
- msg = &node->msg.iotlb;
+ if (v2) {
+ node->msg_v2.type = VHOST_IOTLB_MSG_V2;
+ msg = &node->msg_v2.iotlb;
+ } else {
+ msg = &node->msg.iotlb;
+ }
+
msg->type = VHOST_IOTLB_MISS;
msg->iova = iova;
msg->perm = access;
