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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: 6b1e6cc785 ("vhost: new device IOTLB API")
Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Jason Wang 2018-08-06 11:17:47 +08:00 committed by David S. Miller
parent 9c2e955c48
commit 429711aec2
4 changed files with 111 additions and 19 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

30
drivers/vhost/net.c
View File

@ -77,6 +77,10 @@ enum {
(1ULL << VIRTIO_F_IOMMU_PLATFORM)
};
enum {
VHOST_NET_BACKEND_FEATURES = (1ULL << VHOST_BACKEND_F_IOTLB_MSG_V2)
};
enum {
VHOST_NET_VQ_RX = 0,
VHOST_NET_VQ_TX = 1,
@ -1399,6 +1403,21 @@ done:
return err;
}
static int vhost_net_set_backend_features(struct vhost_net *n, u64 features)
{
int i;
mutex_lock(&n->dev.mutex);
for (i = 0; i < VHOST_NET_VQ_MAX; ++i) {
mutex_lock(&n->vqs[i].vq.mutex);
n->vqs[i].vq.acked_backend_features = features;
mutex_unlock(&n->vqs[i].vq.mutex);
}
mutex_unlock(&n->dev.mutex);
return 0;
}
static int vhost_net_set_features(struct vhost_net *n, u64 features)
{
size_t vhost_hlen, sock_hlen, hdr_len;
@ -1489,6 +1508,17 @@ static long vhost_net_ioctl(struct file *f, unsigned int ioctl,
if (features & ~VHOST_NET_FEATURES)
return -EOPNOTSUPP;
return vhost_net_set_features(n, features);
case VHOST_GET_BACKEND_FEATURES:
features = VHOST_NET_BACKEND_FEATURES;
if (copy_to_user(featurep, &features, sizeof(features)))
return -EFAULT;
return 0;
case VHOST_SET_BACKEND_FEATURES:
if (copy_from_user(&features, featurep, sizeof(features)))
return -EFAULT;
if (features & ~VHOST_NET_BACKEND_FEATURES)
return -EOPNOTSUPP;
return vhost_net_set_backend_features(n, features);
case VHOST_RESET_OWNER:
return vhost_net_reset_owner(n);
case VHOST_SET_OWNER:

71
drivers/vhost/vhost.c
View File

@ -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;

11
drivers/vhost/vhost.h
View File

@ -132,6 +132,7 @@ struct vhost_virtqueue {
struct vhost_umem *iotlb;
void *private_data;
u64 acked_features;
u64 acked_backend_features;
/* Log write descriptors */
void __user *log_base;
struct vhost_log *log;
@ -147,7 +148,10 @@ struct vhost_virtqueue {
};
struct vhost_msg_node {
struct vhost_msg msg;
union {
struct vhost_msg msg;
struct vhost_msg_v2 msg_v2;
};
struct vhost_virtqueue *vq;
struct list_head node;
};
@ -238,6 +242,11 @@ static inline bool vhost_has_feature(struct vhost_virtqueue *vq, int bit)
return vq->acked_features & (1ULL << bit);
}
static inline bool vhost_backend_has_feature(struct vhost_virtqueue *vq, int bit)
{
return vq->acked_backend_features & (1ULL << bit);
}
#ifdef CONFIG_VHOST_CROSS_ENDIAN_LEGACY
static inline bool vhost_is_little_endian(struct vhost_virtqueue *vq)
{

18
include/uapi/linux/vhost.h
View File

@ -65,6 +65,7 @@ struct vhost_iotlb_msg {
};
#define VHOST_IOTLB_MSG 0x1
#define VHOST_IOTLB_MSG_V2 0x2
struct vhost_msg {
int type;
@ -74,6 +75,15 @@ struct vhost_msg {
};
};
struct vhost_msg_v2 {
__u32 type;
__u32 reserved;
union {
struct vhost_iotlb_msg iotlb;
__u8 padding[64];
};
};
struct vhost_memory_region {
__u64 guest_phys_addr;
__u64 memory_size; /* bytes */
@ -160,6 +170,14 @@ struct vhost_memory {
#define VHOST_GET_VRING_BUSYLOOP_TIMEOUT _IOW(VHOST_VIRTIO, 0x24, \
struct vhost_vring_state)
/* Set or get vhost backend capability */
/* Use message type V2 */
#define VHOST_BACKEND_F_IOTLB_MSG_V2 0x1
#define VHOST_SET_BACKEND_FEATURES _IOW(VHOST_VIRTIO, 0x25, __u64)
#define VHOST_GET_BACKEND_FEATURES _IOW(VHOST_VIRTIO, 0x26, __u64)
/* VHOST_NET specific defines */
/* Attach virtio net ring to a raw socket, or tap device.