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).
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| @@ -65,6 +65,7 @@ struct vhost_iotlb_msg { · 64 unmodified lines | |||
| 65 | }; | 65 | }; |
| 66 | 66 | ||
| 67 | #define VHOST_IOTLB_MSG 0x1 | 67 | #define VHOST_IOTLB_MSG 0x1 |
| 68 | #define VHOST_IOTLB_MSG_V2 0x2 | ||
| 68 | 69 | ||
| 69 | struct vhost_msg { | 70 | struct vhost_msg { |
| 70 | int type; | 71 | int type; |
| @@ -74,6 +75,15 @@ struct vhost_msg { · 3 unmodified lines | |||
| 74 | }; | 75 | }; |
| 75 | }; | 76 | }; |
| 76 | 77 | ||
| 78 | struct vhost_msg_v2 { | ||
| 79 | __u32 type; | ||
| 80 | __u32 reserved; | ||
| 81 | union { | ||
| 82 | struct vhost_iotlb_msg iotlb; | ||
| 83 | __u8 padding[64]; | ||
| 84 | }; | ||
| 85 | }; | ||
| 86 | |||
| 77 | struct vhost_memory_region { | 87 | struct vhost_memory_region { |
| 78 | __u64 guest_phys_addr; | 88 | __u64 guest_phys_addr; |
| 79 | __u64 memory_size; /* bytes */ | 89 | __u64 memory_size; /* bytes */ |
| @@ -160,6 +170,14 @@ struct vhost_memory { · 80 unmodified lines | |||
| 160 | #define VHOST_GET_VRING_BUSYLOOP_TIMEOUT _IOW(VHOST_VIRTIO, 0x24, \ | 170 | #define VHOST_GET_VRING_BUSYLOOP_TIMEOUT _IOW(VHOST_VIRTIO, 0x24, \ |
| 161 | struct vhost_vring_state) | 171 | struct vhost_vring_state) |
| 162 | 172 | ||
| 173 | /* Set or get vhost backend capability */ | ||
| 174 | |||
| 175 | /* Use message type V2 */ | ||
| 176 | #define VHOST_BACKEND_F_IOTLB_MSG_V2 0x1 | ||
| 177 | |||
| 178 | #define VHOST_SET_BACKEND_FEATURES _IOW(VHOST_VIRTIO, 0x25, __u64) | ||
| 179 | #define VHOST_GET_BACKEND_FEATURES _IOW(VHOST_VIRTIO, 0x26, __u64) | ||
| 180 | |||
| 163 | /* VHOST_NET specific defines */ | 181 | /* VHOST_NET specific defines */ |
| 164 | 182 | ||
| 165 | /* Attach virtio net ring to a raw socket, or tap device. | 183 | /* Attach virtio net ring to a raw socket, or tap device. |