Re: [PATCH v2 26/29] tools/xenstored: mount 9pfs device in stubdom

[Julien Grall <julien@xxxxxxx>]

Hi Juergen,

On 10/11/2023 16:08, Juergen Gross wrote:
> diff --git a/tools/xenstored/domain.c b/tools/xenstored/domain.c
> index 162b87b460..4263c1360f 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 202d70387a..fddbede869 100644
> --- a/tools/xenstored/minios.c
> +++ b/tools/xenstored/minios.c
> @@ -19,8 +19,16 @@
>   #include <sys/mman.h>
>   #include "core.h"
>   #include <xen/grant_table.h>
> +#include <mini-os/9pfront.h>
>   #include <mini-os/events.h>
>   #include <mini-os/gnttab.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 write_pidfile(const char *pidfile)
>   {
> @@ -62,3 +70,31 @@ void early_init(void)
>         if (stub_domid == DOMID_INVALID)
>                 barf("could not get own domid");
>   }
> +
> +static void mount_thread(void *p)
> +{
> +       xenbus_event_queue events = NULL;
> +       char *err;
> +       char *dummy;
> +
> +       free(xenbus_watch_path_token(XBT_NIL, P9_STATE_PATH, "9pfs", &events));
AFAICT, xenbus_watch_path_token() can fail. I agree this is unlikely, 
but if it fails, then it would be useful to get some logs. Otherwise...
> +
> +       for (;;) {
... this loop would be infinite.

> +               xenbus_wait_for_watch(&events);
> +               err = xenbus_read(XBT_NIL, P9_STATE_PATH, &dummy);
Can you explain why don't care about the value of the node?

> +               if (!err)
> +                       break;
> +               free(err);
> +       }
> +
> +       free(dummy);
> +
> +       free(xenbus_unwatch_path_token(XBT_NIL, P9_STATE_PATH, "9pfs"));
xenbus_unwatch_path_token() could technically fails. It would be helpful 
to print a message.
> +
> +       p9_device = init_9pfront(0, XENSTORE_LIB_DIR);
> +}
> +
> +void mount_9pfs(void)
> +{
> +       create_thread("mount-9pfs", mount_thread, NULL);
> +}
Cheers,

--
Julien Grall