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