diff options
| -rw-r--r-- | docs/specs/vhost-user.txt | 26 | ||||
| -rw-r--r-- | hw/virtio/vhost-user.c | 32 |
2 files changed, 58 insertions, 0 deletions
diff --git a/docs/specs/vhost-user.txt b/docs/specs/vhost-user.txt index 777c49cfe6..7890d71698 100644 --- a/docs/specs/vhost-user.txt +++ b/docs/specs/vhost-user.txt @@ -37,6 +37,8 @@ consists of 3 header fields and a payload: * Flags: 32-bit bit field: - Lower 2 bits are the version (currently 0x01) - Bit 2 is the reply flag - needs to be sent on each reply from the slave + - Bit 3 is the need_reply flag - see VHOST_USER_PROTOCOL_F_REPLY_ACK for + details. * Size - 32-bit size of the payload @@ -126,6 +128,8 @@ the ones that do: * VHOST_GET_VRING_BASE * VHOST_SET_LOG_BASE (if VHOST_USER_PROTOCOL_F_LOG_SHMFD) +[ Also see the section on REPLY_ACK protocol extension. ] + There are several messages that the master sends with file descriptors passed in the ancillary data: @@ -254,6 +258,7 @@ Protocol features #define VHOST_USER_PROTOCOL_F_MQ 0 #define VHOST_USER_PROTOCOL_F_LOG_SHMFD 1 #define VHOST_USER_PROTOCOL_F_RARP 2 +#define VHOST_USER_PROTOCOL_F_REPLY_ACK 3 Message types ------------- @@ -464,3 +469,24 @@ Message types is present in VHOST_USER_GET_PROTOCOL_FEATURES. The first 6 bytes of the payload contain the mac address of the guest to allow the vhost user backend to construct and broadcast the fake RARP. + +VHOST_USER_PROTOCOL_F_REPLY_ACK: +------------------------------- +The original vhost-user specification only demands replies for certain +commands. This differs from the vhost protocol implementation where commands +are sent over an ioctl() call and block until the client has completed. + +With this protocol extension negotiated, the sender (QEMU) can set the +"need_reply" [Bit 3] flag to any command. This indicates that +the client MUST respond with a Payload VhostUserMsg indicating success or +failure. The payload should be set to zero on success or non-zero on failure, +unless the message already has an explicit reply body. + +The response payload gives QEMU a deterministic indication of the result +of the command. Today, QEMU is expected to terminate the main vhost-user +loop upon receiving such errors. In future, qemu could be taught to be more +resilient for selective requests. + +For the message types that already solicit a reply from the client, the +presence of VHOST_USER_PROTOCOL_F_REPLY_ACK or need_reply bit being set brings +no behavioural change. (See the 'Communication' section for details.) diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c index 1995fd20bd..b57454a4b7 100644 --- a/hw/virtio/vhost-user.c +++ b/hw/virtio/vhost-user.c @@ -31,6 +31,7 @@ enum VhostUserProtocolFeature { VHOST_USER_PROTOCOL_F_MQ = 0, VHOST_USER_PROTOCOL_F_LOG_SHMFD = 1, VHOST_USER_PROTOCOL_F_RARP = 2, + VHOST_USER_PROTOCOL_F_REPLY_ACK = 3, VHOST_USER_PROTOCOL_F_MAX }; @@ -84,6 +85,7 @@ typedef struct VhostUserMsg { #define VHOST_USER_VERSION_MASK (0x3) #define VHOST_USER_REPLY_MASK (0x1<<2) +#define VHOST_USER_NEED_REPLY_MASK (0x1 << 3) uint32_t flags; uint32_t size; /* the following payload size */ union { @@ -158,6 +160,25 @@ fail: return -1; } +static int process_message_reply(struct vhost_dev *dev, + VhostUserRequest request) +{ + VhostUserMsg msg; + + if (vhost_user_read(dev, &msg) < 0) { + return -1; + } + + if (msg.request != request) { + error_report("Received unexpected msg type." + "Expected %d received %d", + request, msg.request); + return -1; + } + + return msg.payload.u64 ? -1 : 0; +} + static bool vhost_user_one_time_request(VhostUserRequest request) { switch (request) { @@ -248,11 +269,18 @@ static int vhost_user_set_mem_table(struct vhost_dev *dev, int fds[VHOST_MEMORY_MAX_NREGIONS]; int i, fd; size_t fd_num = 0; + bool reply_supported = virtio_has_feature(dev->protocol_features, + VHOST_USER_PROTOCOL_F_REPLY_ACK); + VhostUserMsg msg = { .request = VHOST_USER_SET_MEM_TABLE, .flags = VHOST_USER_VERSION, }; + if (reply_supported) { + msg.flags |= VHOST_USER_NEED_REPLY_MASK; + } + for (i = 0; i < dev->mem->nregions; ++i) { struct vhost_memory_region *reg = dev->mem->regions + i; ram_addr_t offset; @@ -288,6 +316,10 @@ static int vhost_user_set_mem_table(struct vhost_dev *dev, return -1; } + if (reply_supported) { + return process_message_reply(dev, msg.request); + } + return 0; } |