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vhost: switch to use new message format

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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
Download Patch File Download Diff File Expand all files Collapse all files

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.