[xen staging] tools/xenstored: mount 9pfs device in stubdom

[patchbot@xxxxxxx]

commit 0a999849c82e9e3c060280cc6c3362f86d96cf26
Author:     Juergen Gross <jgross@xxxxxxxx>
AuthorDate: Thu Feb 29 13:48:27 2024 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Thu Feb 29 17:00:04 2024 +0100

    tools/xenstored: mount 9pfs device in stubdom
    
    Mount the 9pfs device in stubdom enabling it to use files.
    
    This has to happen in a worker thread in order to allow the main thread
    handling the required Xenstore accesses in parallel.
    
    Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
    Reviewed-by: Jason Andryuk <jandryuk@xxxxxxxxx>
    Reviewed-by: Julien Grall <jgrall@xxxxxxxxxx>
---
 tools/xenstored/core.h   |  6 ++++++
 tools/xenstored/domain.c |  2 ++
 tools/xenstored/minios.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 62 insertions(+)

diff --git a/tools/xenstored/core.h b/tools/xenstored/core.h
index f6af086f01..fe0ee90581 100644
--- a/tools/xenstored/core.h
+++ b/tools/xenstored/core.h
@@ -36,6 +36,8 @@
 #include "list.h"
 #include "hashtable.h"
 
+#define XENSTORE_LIB_DIR       XEN_LIB_DIR "/xenstore"
+
 #ifndef O_CLOEXEC
 #define O_CLOEXEC 0
 /* O_CLOEXEC support is needed for Live Update in the daemon case. */
@@ -399,6 +401,10 @@ void handle_special_fds(void);
 int get_socket_fd(void);
 void set_socket_fd(int fd);
 
+#ifdef __MINIOS__
+void mount_9pfs(void);
+#endif
+
 /* Close stdin/stdout/stderr to complete daemonize */
 void finish_daemonize(void);
 
diff --git a/tools/xenstored/domain.c b/tools/xenstored/domain.c
index 1a7d5e9756..64c8fd0cc3 100644
--- a/tools/xenstored/domain.c
+++ b/tools/xenstored/domain.c
@@ -1236,6 +1236,8 @@ void stubdom_init(void)
                barf_perror("Failed to initialize stubdom");
 
        xenevtchn_notify(xce_handle, stubdom->port);
+
+       mount_9pfs();
 #endif
 }
 
diff --git a/tools/xenstored/minios.c b/tools/xenstored/minios.c
index 22ac8defbd..562a9b4972 100644
--- a/tools/xenstored/minios.c
+++ b/tools/xenstored/minios.c
@@ -17,10 +17,20 @@
 */
 #include <sys/types.h>
 #include <sys/mman.h>
+#include <syslog.h>
+#include "talloc.h"
 #include "core.h"
 #include "utils.h"
 #include <xen/grant_table.h>
 #include <mini-os/lib.h>
+#include <mini-os/9pfront.h>
+#include <mini-os/sched.h>
+#include <mini-os/xenbus.h>
+#include <mini-os/xmalloc.h>
+
+#define P9_STATE_PATH  "device/9pfs/0/state"
+
+static void *p9_device;
 
 void finish_daemonize(void)
 {
@@ -74,3 +84,47 @@ int get_socket_fd(void)
 void set_socket_fd(int fd)
 {
 }
+
+static void mount_thread(void *p)
+{
+       xenbus_event_queue events = NULL;
+       char *err;
+       char *dummy;
+
+       err = xenbus_watch_path_token(XBT_NIL, P9_STATE_PATH, "9pfs", &events);
+       if (err) {
+               log("error \"%s\" when setting watch on \"%s\"\n", err,
+                   P9_STATE_PATH);
+               free(err);
+               return;
+       }
+
+       for (;;) {
+               xenbus_wait_for_watch(&events);
+
+               /*
+                * We only care for existence of the state node.
+                * State changes are handled in init_9pfront().
+                */
+               err = xenbus_read(XBT_NIL, P9_STATE_PATH, &dummy);
+               if (!err)
+                       break;
+               free(err);
+       }
+
+       free(dummy);
+
+       err = xenbus_unwatch_path_token(XBT_NIL, P9_STATE_PATH, "9pfs");
+       if (err) {
+               log("error \"%s\" when unwatching \"%s\", leaking watch\n",
+                   err, P9_STATE_PATH);
+               free(err);
+       }
+
+       p9_device = init_9pfront(0, XENSTORE_LIB_DIR);
+}
+
+void mount_9pfs(void)
+{
+       create_thread("mount-9pfs", mount_thread, NULL);
+}
--
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