On 2025-07-25 02:41, Jürgen Groß wrote:
On 25.07.25 04:28, Jason Andryuk wrote:
Add a helper to lookup the event channel for a domid. This hides some
of the differences between dom0 and stubdom xenstored.
It highlights the different meanings between get_xenbus_evtchn() in a
stubdom, where it looks up dom0's event channel, and dom0, where it
looks up the local event channel.
The default return 0 will be fine as any other auto-introduced domain
will needs the event channel populated in the grant.
Signed-off-by: Jason Andryuk <jason.andr...@amd.com>
---
tools/xenstored/domain.c | 38 ++++++++++++++++++++++++++++++++++++--
1 file changed, 36 insertions(+), 2 deletions(-)
diff --git a/tools/xenstored/domain.c b/tools/xenstored/domain.c
index 1241f8c73e..1c52254ba8 100644
--- a/tools/xenstored/domain.c
+++ b/tools/xenstored/domain.c
@@ -1251,12 +1251,41 @@ const char *get_implicit_path(const struct
connection *conn)
return conn->domain->path;
}
+/*
+ * dom0 xenstored (posix.c) uses get_xenbus_evtchn() to lookup with
+ * XENSTORED_PORT_DEV.
+ *
+ * minios stubdom uses get_xenbus_evtchn() to look up dom0's event
channel
+ * from the command line (--event). The stubdom's own event channel is
+ * returned directly.
+ *
+ * Any other existing domains from dom0less/Hyperlaunch will have
+ * the event channel in the xenstore page, so lookup here isn't
necessary.
+ * --event would not be set, so it would default to 0.
+ */
+evtchn_port_t get_domain_evtchn(domid_t domid)
+{
+#ifdef __MINIOS__
+ if (domid == stub_domid) {
+ return xenbus_evtchn;
+ } else if (domid == priv_domid) {
+ return get_xenbus_evtchn();
+ }
+#else
+ if (domid == xenbus_master_domid()) {
+ return get_xenbus_evtchn();
+ }
+#endif
+
+ return 0;
+}
+
I'd prefer to have 2 get_domain_evtchn() variants, one in posix.c and
one in minios.c. This way you can avoid the #ifdef.
Sounds good.
void dom0_init(void)
{
evtchn_port_t port;
struct domain *dom0;
- port = get_xenbus_evtchn();
+ port = get_domain_evtchn(xenbus_master_domid());
if (port == -1)
barf_perror("Failed to initialize dom0 port");
@@ -1271,11 +1300,16 @@ void stubdom_init(void)
{
#ifdef __MINIOS__
struct domain *stubdom;
+ evtchn_port_t port;
if (stub_domid < 0)
return;
- stubdom = introduce_domain(NULL, stub_domid, xenbus_evtchn, false);
+ port = get_domain_evtchn(stub_domid);
+ if (port == -1)
+ barf_perror("Failed to initialize dom0 port");
s/dom0/stubdom/
Thanks,
Jason
