On 14.10.25 10:30, Marc-André Lureau wrote:
Hi
On Mon, Oct 13, 2025 at 5:39 PM Vladimir Sementsov-Ogievskiy
<[email protected]> wrote:
Give vhost-user-blk a possibility (and responsibility) to decide when
do connect. It will help us to realize vhost-user-blk backend-transfer
migration feature:
For incoming migration we'll need to postpone connect at least until
early stage of migrate-incoming command, when we already know all
migration parameters and can decide, are we going to do incoming
backend-transfer (and get chardev fd from incoming stream), or we
finally need to connect.
With this patch, we don't modify vhost-user-blk.c: it already
do call qemu_chr_fe_wait_connected(), which in turn calls
qemu_chr_connect().
Signed-off-by: Vladimir Sementsov-Ogievskiy <[email protected]>
---
chardev/char-fe.c | 21 +++++++++++++++++----
hw/core/qdev-properties-system.c | 2 +-
include/chardev/char-fe.h | 2 ++
3 files changed, 20 insertions(+), 5 deletions(-)
diff --git a/chardev/char-fe.c b/chardev/char-fe.c
index 973fed5bea..9e2c658cb9 100644
--- a/chardev/char-fe.c
+++ b/chardev/char-fe.c
@@ -189,12 +189,20 @@ bool qemu_chr_fe_backend_open(CharBackend *be)
return be->chr && be->chr->be_open;
}
-bool qemu_chr_fe_init(CharBackend *b, Chardev *s, Error **errp)
+bool qemu_chr_fe_init_ex(CharBackend *b, Chardev *s, ObjectClass *oc,
+ Error **errp)
{
unsigned int tag = 0;
-
- if (!qemu_chr_connect(s, errp)) {
- return false;
+ const char *driver = oc ? object_class_get_name(oc) : NULL;
+
+ /*
+ * vhost-user-blk wants call qemu_chr_connect by hand,
+ * to support backend-transfer migration feature.
+ */
+ if (!driver || !g_str_has_prefix(driver, "vhost-user-blk")) {
+ if (!qemu_chr_connect(s, errp)) {
+ return false;
+ }
Why not pass a bool "connect" instead?
DEFINE_PROP_CHR() would use "true".
+ Introduce DEFINE_PROP_CHR_NO_CONNECT() that would use "false".
and wire it with a new PropertyInfo and modified callbacks.
Will try, thanks for idea. I don't like this checking by name too, just design
it after
.check_peer_type in net/ code.
}
if (s) {
@@ -218,6 +226,11 @@ bool qemu_chr_fe_init(CharBackend *b, Chardev *s, Error
**errp)
return true;
}
+bool qemu_chr_fe_init(CharBackend *b, Chardev *s, Error **errp)
+{
+ return qemu_chr_fe_init_ex(b, s, NULL, errp);
+}
+
void qemu_chr_fe_deinit(CharBackend *b, bool del)
{
assert(b);
diff --git a/hw/core/qdev-properties-system.c b/hw/core/qdev-properties-system.c
index 1f810b7ddf..35eed17d4d 100644
--- a/hw/core/qdev-properties-system.c
+++ b/hw/core/qdev-properties-system.c
@@ -297,7 +297,7 @@ static void set_chr(Object *obj, Visitor *v, const char
*name, void *opaque,
if (s == NULL) {
error_setg(errp, "Property '%s.%s' can't find value '%s'",
object_get_typename(obj), name, str);
- } else if (!qemu_chr_fe_init(be, s, errp)) {
+ } else if (!qemu_chr_fe_init_ex(be, s, obj->class, errp)) {
error_prepend(errp, "Property '%s.%s' can't take value '%s': ",
object_get_typename(obj), name, str);
}
diff --git a/include/chardev/char-fe.h b/include/chardev/char-fe.h
index 8ef05b3dd0..f1c05cc5ed 100644
--- a/include/chardev/char-fe.h
+++ b/include/chardev/char-fe.h
@@ -34,6 +34,8 @@ struct CharBackend {
* Returns: false on error.
*/
bool qemu_chr_fe_init(CharBackend *b, Chardev *s, Error **errp);
+bool qemu_chr_fe_init_ex(CharBackend *b, Chardev *s, ObjectClass *oc,
+ Error **errp);
/**
* qemu_chr_fe_deinit:
--
2.48.1
--
Best regards,
Vladimir
