[Xen-devel] [PATCH v2] xen: write information about supported backends

[Juergen Gross <jgross@xxxxxxxx>]

Add a Xenstore directory for each supported pv backend. This will allow
Xen tools to decide which backend type to use in case there are
multiple possibilities.

The information is added under
/local/domain/<backend-domid>/device-model/<domid>/backends
before the "running" state is written to Xenstore. Using a directory
for each backend enables us to add parameters for specific backends
in the future.

This interface is documented in the Xen source repository in the file
docs/misc/qemu-backends.txt

In order to reuse the Xenstore directory creation already present in
hw/xen/xen_devconfig.c move the related functions to
hw/xen/xen_backend.c where they fit better.

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
V2: update commit message as requested by Stefano
---
 hw/xen/xen_backend.c         | 52 ++++++++++++++++++++++++++++++++++++++++++++
 hw/xen/xen_devconfig.c       | 52 ++------------------------------------------
 include/hw/xen/xen_backend.h |  1 +
 3 files changed, 55 insertions(+), 50 deletions(-)

diff --git a/hw/xen/xen_backend.c b/hw/xen/xen_backend.c
index 60575ad..8983440 100644
--- a/hw/xen/xen_backend.c
+++ b/hw/xen/xen_backend.c
@@ -42,11 +42,35 @@ struct xs_handle *xenstore = NULL;
 const char *xen_protocol;
 
 /* private */
+struct xs_dirs {
+    char *xs_dir;
+    QTAILQ_ENTRY(xs_dirs) list;
+};
+static QTAILQ_HEAD(xs_dirs_head, xs_dirs) xs_cleanup = 
QTAILQ_HEAD_INITIALIZER(xs_cleanup);
+
 static QTAILQ_HEAD(XenDeviceHead, XenDevice) xendevs = 
QTAILQ_HEAD_INITIALIZER(xendevs);
 static int debug = 0;
 
 /* ------------------------------------------------------------- */
 
+static void xenstore_cleanup_dir(char *dir)
+{
+    struct xs_dirs *d;
+
+    d = g_malloc(sizeof(*d));
+    d->xs_dir = dir;
+    QTAILQ_INSERT_TAIL(&xs_cleanup, d, list);
+}
+
+void xen_config_cleanup(void)
+{
+    struct xs_dirs *d;
+
+    QTAILQ_FOREACH(d, &xs_cleanup, list) {
+        xs_rm(xenstore, 0, d->xs_dir);
+    }
+}
+
 int xenstore_write_str(const char *base, const char *node, const char *val)
 {
     char abspath[XEN_BUFSIZE];
@@ -75,6 +99,28 @@ char *xenstore_read_str(const char *base, const char *node)
     return ret;
 }
 
+int xenstore_mkdir(char *path, int p)
+{
+    struct xs_permissions perms[2] = {{
+            .id    = 0, /* set owner: dom0 */
+        },{
+            .id    = xen_domid,
+            .perms = p,
+        }};
+
+    if (!xs_mkdir(xenstore, 0, path)) {
+        xen_be_printf(NULL, 0, "xs_mkdir %s: failed\n", path);
+        return -1;
+    }
+    xenstore_cleanup_dir(g_strdup(path));
+
+    if (!xs_set_permissions(xenstore, 0, path, perms, 2)) {
+        xen_be_printf(NULL, 0, "xs_set_permissions %s: failed\n", path);
+        return -1;
+    }
+    return 0;
+}
+
 int xenstore_write_int(const char *base, const char *node, int ival)
 {
     char val[12];
@@ -726,6 +772,12 @@ err:
 
 int xen_be_register(const char *type, struct XenDevOps *ops)
 {
+    char path[50];
+
+    snprintf(path, sizeof (path), "device-model/%u/backends/%s", xen_domid,
+             type);
+    xenstore_mkdir(path, XS_PERM_READ);
+
     return xenstore_scan(type, xen_domid, ops);
 }
 
diff --git a/hw/xen/xen_devconfig.c b/hw/xen/xen_devconfig.c
index 1f30fe4..b7d290d 100644
--- a/hw/xen/xen_devconfig.c
+++ b/hw/xen/xen_devconfig.c
@@ -5,54 +5,6 @@
 
 /* ------------------------------------------------------------- */
 
-struct xs_dirs {
-    char *xs_dir;
-    QTAILQ_ENTRY(xs_dirs) list;
-};
-static QTAILQ_HEAD(xs_dirs_head, xs_dirs) xs_cleanup = 
QTAILQ_HEAD_INITIALIZER(xs_cleanup);
-
-static void xen_config_cleanup_dir(char *dir)
-{
-    struct xs_dirs *d;
-
-    d = g_malloc(sizeof(*d));
-    d->xs_dir = dir;
-    QTAILQ_INSERT_TAIL(&xs_cleanup, d, list);
-}
-
-void xen_config_cleanup(void)
-{
-    struct xs_dirs *d;
-
-    QTAILQ_FOREACH(d, &xs_cleanup, list) {
-       xs_rm(xenstore, 0, d->xs_dir);
-    }
-}
-
-/* ------------------------------------------------------------- */
-
-static int xen_config_dev_mkdir(char *dev, int p)
-{
-    struct xs_permissions perms[2] = {{
-            .id    = 0, /* set owner: dom0 */
-        },{
-            .id    = xen_domid,
-            .perms = p,
-        }};
-
-    if (!xs_mkdir(xenstore, 0, dev)) {
-       xen_be_printf(NULL, 0, "xs_mkdir %s: failed\n", dev);
-       return -1;
-    }
-    xen_config_cleanup_dir(g_strdup(dev));
-
-    if (!xs_set_permissions(xenstore, 0, dev, perms, 2)) {
-       xen_be_printf(NULL, 0, "xs_set_permissions %s: failed\n", dev);
-       return -1;
-    }
-    return 0;
-}
-
 static int xen_config_dev_dirs(const char *ftype, const char *btype, int vdev,
                               char *fe, char *be, int len)
 {
@@ -66,8 +18,8 @@ static int xen_config_dev_dirs(const char *ftype, const char 
*btype, int vdev,
     snprintf(be, len, "%s/backend/%s/%d/%d", dom, btype, xen_domid, vdev);
     free(dom);
 
-    xen_config_dev_mkdir(fe, XS_PERM_READ | XS_PERM_WRITE);
-    xen_config_dev_mkdir(be, XS_PERM_READ);
+    xenstore_mkdir(fe, XS_PERM_READ | XS_PERM_WRITE);
+    xenstore_mkdir(be, XS_PERM_READ);
     return 0;
 }
 
diff --git a/include/hw/xen/xen_backend.h b/include/hw/xen/xen_backend.h
index b4b4ff0..1bc5042 100644
--- a/include/hw/xen/xen_backend.h
+++ b/include/hw/xen/xen_backend.h
@@ -63,6 +63,7 @@ extern const char *xen_protocol;
 extern DeviceState *xen_sysdev;
 
 /* xenstore helper functions */
+int xenstore_mkdir(char *path, int p);
 int xenstore_write_str(const char *base, const char *node, const char *val);
 int xenstore_write_int(const char *base, const char *node, int ival);
 int xenstore_write_int64(const char *base, const char *node, int64_t ival);
-- 
2.6.6


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