Fixes: 2b8819c6eee5 ("vhost-user: modify SET_LOG_BASE to pass mmap size and
offset")
For compatibility with old vhost backend content of the SET_LOG_BASE message
can not be modified.
The SET_LOG_BASE message payload is modified only if the
VHOST_USER_PROTOCOL_F_LOG_SHMFD protocol feature has been negociated.
The documentation has been updated accordingly with remarks from Marc André
Lureau.
Signed-off-by: Thibaut Collet <thibaut.col...@6wind.com>
---
docs/specs/vhost-user.txt | 16 ++++++++++++++--
hw/virtio/vhost-user.c | 12 +++++++++---
2 files changed, 23 insertions(+), 5 deletions(-)
diff --git a/docs/specs/vhost-user.txt b/docs/specs/vhost-user.txt
index 26dde2e..da4bf9c 100644
--- a/docs/specs/vhost-user.txt
+++ b/docs/specs/vhost-user.txt
@@ -87,6 +87,14 @@ Depending on the request type, payload can be:
User address: a 64-bit user address
mmap offset: 64-bit offset where region starts in the mapped memory
+ * vhost user log description
+ -----------------
+ | size | offset |
+ -----------------
+
+ size: a 64-bit size
+ Offset: a 64-bit offset where log starts in the mapped memory
+
In QEMU the vhost-user message is implemented with the following struct:
typedef struct VhostUserMsg {
@@ -280,14 +288,18 @@ Message types
Id: 6
Equivalent ioctl: VHOST_SET_LOG_BASE
- Master payload: u64
+ Master payload: - u64 if slave has not the
VHOST_USER_PROTOCOL_F_LOG_SHMFD
+ protocol feature
+ - vhost user log if slave has the
+ VHOST_USER_PROTOCOL_F_LOG_SHMFD protocol feature
Slave payload: N/A
Sets logging shared memory space.
When slave has VHOST_USER_PROTOCOL_F_LOG_SHMFD protocol
feature, the log memory fd is provided in the ancillary data of
VHOST_USER_SET_LOG_BASE message, the size and offset of shared
- memory area provided in the message.
+ memory area provided in the message and the message reply is an
+ empty message (size of 0).
* VHOST_USER_SET_LOG_FD
diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
index c443602..dcdfd40 100644
--- a/hw/virtio/vhost-user.c
+++ b/hw/virtio/vhost-user.c
@@ -206,11 +206,17 @@ static int vhost_user_set_log_base(struct vhost_dev *dev,
uint64_t base,
VhostUserMsg msg = {
.request = VHOST_USER_SET_LOG_BASE,
.flags = VHOST_USER_VERSION,
- .payload.log.mmap_size = log->size,
- .payload.log.mmap_offset = 0,
- .size = sizeof(msg.payload.log),
};
+ if (shmfd) {
+ msg.payload.log.mmap_size = log->size;
+ msg.payload.log.mmap_offset = 0;
+ msg.size = sizeof(msg.payload.log);
+ } else {
+ msg.payload.u64 = base;
+ msg.size = sizeof(msg.payload.u64);
+ }
+
if (shmfd && log->fd != -1) {
fds[fd_num++] = log->fd;
}
--
2.1.4
