[PATCH v8 4/8] tools: add 9pfs device to xenstore-stubdom

[Juergen Gross <jgross@xxxxxxxx>]

Add a 9pfs device to Xenstore stubdom in order to allow it to do e.g.
logging into a dom0 file.

Use the following parameters for the new device:

- tag = "Xen"
- type = "xen_9pfsd"
- path = "/var/lib/xen/xenstore"
- security-model = "none"

For now don't limit allowed file space or number of files.

Add a new libxl function for adding it similar to the function for
adding the console device.

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
Reviewed-by: Jason Andryuk <jandryuk@xxxxxxxxx>
Reviewed-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>
---
V2:
- add security_model parameter to new libxl function (Jason Andryuk)
V4:
- rename function to libxl_device_9pfs_add() (Anthony Perard)
- use a libxl_device_p9 pointer as parameter (Anthony Perard)
V8:
- remove "_XENSTORE" suffix from define (Anthony Perard)
---
 tools/helpers/init-xenstore-domain.c |  7 +++++++
 tools/include/libxl.h                | 15 +++++++++++++++
 tools/libs/light/libxl_9pfs.c        | 16 ++++++++++++++++
 3 files changed, 38 insertions(+)

diff --git a/tools/helpers/init-xenstore-domain.c 
b/tools/helpers/init-xenstore-domain.c
index 140ed610ae..1683438c5c 100644
--- a/tools/helpers/init-xenstore-domain.c
+++ b/tools/helpers/init-xenstore-domain.c
@@ -433,6 +433,12 @@ int main(int argc, char** argv)
     int rv, fd;
     char *maxmem_str = NULL;
     libxl_ctx *ctx;
+    libxl_device_p9 p9 = { .backend_domid = 0,
+                           .tag = "Xen",
+                           .path = XEN_LIB_DIR"/xenstore",
+                           .security_model = "none",
+                           .type = LIBXL_P9_TYPE_XEN_9PFSD,
+    };
 
     while ( (opt = getopt_long(argc, argv, "v", options, NULL)) != -1 )
     {
@@ -543,6 +549,7 @@ int main(int argc, char** argv)
     }
     libxl_console_add_xenstore(ctx, domid, 0, console_evtchn, console_gfn,
                                NULL);
+    libxl_device_9pfs_add(ctx, domid, &p9, NULL);
     libxl_ctx_free(ctx);
 
     fd = creat(XEN_RUN_DIR "/xenstored.pid", 0666);
diff --git a/tools/include/libxl.h b/tools/include/libxl.h
index 9a3e702557..804496a9f8 100644
--- a/tools/include/libxl.h
+++ b/tools/include/libxl.h
@@ -583,6 +583,13 @@
  * libxl_console_add_xenstore() in libxl.
  */
 #define LIBXL_HAVE_CONSOLE_ADD_XENSTORE 1
+
+/*
+ * LIBXL_HAVE_P9_ADD indicates presence of the function
+ * libxl_device_9pfs_add() in libxl.
+ */
+#define LIBXL_HAVE_P9_ADD 1
+
 /*
  * libxl ABI compatibility
  *
@@ -2074,6 +2081,14 @@ int libxl_console_add_xenstore(libxl_ctx *ctx, uint32_t 
domid, uint32_t backend,
                                const libxl_asyncop_how *ao_how)
                                LIBXL_EXTERNAL_CALLERS_ONLY;
 
+/* libxl_device_9pfs_add writes the Xenstore entries for a domain's
+ * primary 9pfs device based on domid, and device parameters.
+ * If needed it will start the backend daemon.
+ */
+int libxl_device_9pfs_add(libxl_ctx *ctx, uint32_t domid, libxl_device_p9 *p9,
+                          const libxl_asyncop_how *ao_how)
+                          LIBXL_EXTERNAL_CALLERS_ONLY;
+
 /* May be called with info_r == NULL to check for domain's existence.
  * Returns ERROR_DOMAIN_NOTFOUND if domain does not exist (used to return
  * ERROR_INVAL for this scenario). */
diff --git a/tools/libs/light/libxl_9pfs.c b/tools/libs/light/libxl_9pfs.c
index ddeb4f20a7..48f894f070 100644
--- a/tools/libs/light/libxl_9pfs.c
+++ b/tools/libs/light/libxl_9pfs.c
@@ -206,6 +206,22 @@ static void libxl__device_p9_add(libxl__egc *egc, uint32_t 
domid,
         aodev->callback(egc, aodev);
 }
 
+int libxl_device_9pfs_add(libxl_ctx *ctx, uint32_t domid, libxl_device_p9 *p9,
+                          const libxl_asyncop_how *ao_how)
+{
+    AO_CREATE(ctx, domid, ao_how);
+    libxl__ao_device *aodev;
+
+    GCNEW(aodev);
+    libxl__prepare_ao_device(ao, aodev);
+    aodev->action = LIBXL__DEVICE_ACTION_ADD;
+    aodev->callback = device_addrm_aocomplete;
+
+    libxl__device_p9_add(egc, domid, p9, aodev);
+
+    return AO_INPROGRESS;
+}
+
 #define libxl_device_p9_list NULL
 #define libxl_device_p9_compare NULL
 
-- 
2.35.3