[Xen-changelog] [xen master] libxl: add basic support for devices without backend

[patchbot@xxxxxxx]

commit 86741b1f4a2578df3fda7ff73cc208041d5e87b3
Author:     Juergen Gross <jgross@xxxxxxxx>
AuthorDate: Tue Sep 20 16:18:08 2016 +0200
Commit:     Wei Liu <wei.liu2@xxxxxxxxxx>
CommitDate: Tue Sep 20 15:48:42 2016 +0100

    libxl: add basic support for devices without backend
    
    With the planned support of HVM USB passthrough via the USB emulation
    capabilities of qemu libxl has to support guest devices which have no
    back- and frontend. Information about those devices will live in the
    libxl part of Xenstore only.
    
    Add some basic support to libxl to be able to cope with this scenario.
    
    Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
    Acked-by: Wei Liu <wei.liu2@xxxxxxxxxx>
---
 tools/libxl/libxl_device.c           | 70 ++++++++++++++++++++++++------------
 tools/libxl/libxl_types_internal.idl |  1 +
 tools/libxl/libxl_xshelp.c           |  6 +++-
 3 files changed, 53 insertions(+), 24 deletions(-)

diff --git a/tools/libxl/libxl_device.c b/tools/libxl/libxl_device.c
index dbf157d..1cc9098 100644
--- a/tools/libxl/libxl_device.c
+++ b/tools/libxl/libxl_device.c
@@ -114,15 +114,21 @@ int libxl__device_generic_add(libxl__gc *gc, 
xs_transaction_t t,
         libxl__device *device, char **bents, char **fents, char **ro_fents)
 {
     libxl_ctx *ctx = libxl__gc_owner(gc);
-    char *frontend_path, *backend_path, *libxl_path;
+    char *frontend_path = NULL, *backend_path = NULL, *libxl_path;
     struct xs_permissions frontend_perms[2];
     struct xs_permissions ro_frontend_perms[2];
     struct xs_permissions backend_perms[2];
     int create_transaction = t == XBT_NULL;
+    int libxl_only = device->backend_kind == LIBXL__DEVICE_KIND_NONE;
     int rc;
 
-    frontend_path = libxl__device_frontend_path(gc, device);
-    backend_path = libxl__device_backend_path(gc, device);
+    if (libxl_only) {
+        /* bents should be set as this is used to setup libxl_path content. */
+        assert(!fents && !ro_fents);
+    } else {
+        frontend_path = libxl__device_frontend_path(gc, device);
+        backend_path = libxl__device_backend_path(gc, device);
+    }
     libxl_path = libxl__device_libxl_path(gc, device);
 
     frontend_perms[0].id = device->domid;
@@ -144,13 +150,15 @@ retry_transaction:
     rc = libxl__xs_rm_checked(gc, t, libxl_path);
     if (rc) goto out;
 
-    rc = libxl__xs_write_checked(gc, t, GCSPRINTF("%s/frontend",libxl_path),
-                                 frontend_path);
-    if (rc) goto out;
+    if (!libxl_only) {
+        rc = libxl__xs_write_checked(gc, t, 
GCSPRINTF("%s/frontend",libxl_path),
+                                     frontend_path);
+        if (rc) goto out;
 
-    rc = libxl__xs_write_checked(gc, t, GCSPRINTF("%s/backend",libxl_path),
-                                 backend_path);
-    if (rc) goto out;
+        rc = libxl__xs_write_checked(gc, t, GCSPRINTF("%s/backend",libxl_path),
+                                     backend_path);
+        if (rc) goto out;
+    }
 
     /* xxx much of this function lacks error checks! */
 
@@ -179,12 +187,15 @@ retry_transaction:
     }
 
     if (bents) {
-        xs_rm(ctx->xsh, t, backend_path);
-        xs_mkdir(ctx->xsh, t, backend_path);
-        xs_set_permissions(ctx->xsh, t, backend_path, backend_perms, 
ARRAY_SIZE(backend_perms));
-        xs_write(ctx->xsh, t, GCSPRINTF("%s/frontend", backend_path),
-                 frontend_path, strlen(frontend_path));
-        libxl__xs_writev(gc, t, backend_path, bents);
+        if (!libxl_only) {
+            xs_rm(ctx->xsh, t, backend_path);
+            xs_mkdir(ctx->xsh, t, backend_path);
+            xs_set_permissions(ctx->xsh, t, backend_path, backend_perms,
+                               ARRAY_SIZE(backend_perms));
+            xs_write(ctx->xsh, t, GCSPRINTF("%s/frontend", backend_path),
+                     frontend_path, strlen(frontend_path));
+            libxl__xs_writev(gc, t, backend_path, bents);
+        }
 
         /*
          * We make a copy of everything for the backend in the libxl
@@ -194,6 +205,9 @@ retry_transaction:
          * instead.  But there are still places in libxl that try to
          * reconstruct a config from xenstore.
          *
+         * For devices without PV backend (e.g. USB devices emulated via qemu)
+         * only the libxl path is written.
+         *
          * This duplication will typically produces duplicate keys
          * which will go out of date, but that's OK because nothing
          * reads those.  For example, there is usually
@@ -679,14 +693,21 @@ void libxl__multidev_prepared(libxl__egc *egc,
 
 int libxl__device_destroy(libxl__gc *gc, libxl__device *dev)
 {
-    const char *be_path = libxl__device_backend_path(gc, dev);
-    const char *fe_path = libxl__device_frontend_path(gc, dev);
+    const char *be_path = NULL;
+    const char *fe_path = NULL;
     const char *libxl_path = libxl__device_libxl_path(gc, dev);
-    const char *tapdisk_path = GCSPRINTF("%s/%s", be_path, "tapdisk-params");
-    const char *tapdisk_params;
+    const char *tapdisk_path = NULL;
+    const char *tapdisk_params = NULL;
     xs_transaction_t t = 0;
     int rc;
     uint32_t domid;
+    int libxl_only = dev->backend_kind == LIBXL__DEVICE_KIND_NONE;
+
+    if (!libxl_only) {
+        be_path = libxl__device_backend_path(gc, dev);
+        fe_path = libxl__device_frontend_path(gc, dev);
+        tapdisk_path = GCSPRINTF("%s/%s", be_path, "tapdisk-params");
+    }
 
     rc = libxl__get_domid(gc, &domid);
     if (rc) goto out;
@@ -696,18 +717,21 @@ int libxl__device_destroy(libxl__gc *gc, libxl__device 
*dev)
         if (rc) goto out;
 
         /* May not exist if this is not a tap device */
-        rc = libxl__xs_read_checked(gc, t, tapdisk_path, &tapdisk_params);
-        if (rc) goto out;
+        if (tapdisk_path) {
+            rc = libxl__xs_read_checked(gc, t, tapdisk_path, &tapdisk_params);
+            if (rc) goto out;
+        }
 
         if (domid == LIBXL_TOOLSTACK_DOMID) {
             /*
              * The toolstack domain is in charge of removing the
              * frontend and libxl paths.
              */
-            libxl__xs_path_cleanup(gc, t, fe_path);
+            if (!libxl_only)
+                libxl__xs_path_cleanup(gc, t, fe_path);
             libxl__xs_path_cleanup(gc, t, libxl_path);
         }
-        if (dev->backend_domid == domid) {
+        if (dev->backend_domid == domid && !libxl_only) {
             /*
              * The driver domain is in charge of removing what it can
              * from the backend path.
diff --git a/tools/libxl/libxl_types_internal.idl 
b/tools/libxl/libxl_types_internal.idl
index 177f9b7..82e5c07 100644
--- a/tools/libxl/libxl_types_internal.idl
+++ b/tools/libxl/libxl_types_internal.idl
@@ -14,6 +14,7 @@ libxl__qmp_message_type = Enumeration("qmp_message_type", [
     ])
 
 libxl__device_kind = Enumeration("device_kind", [
+    (0, "NONE"),
     (1, "VIF"),
     (2, "VBD"),
     (3, "QDISK"),
diff --git a/tools/libxl/libxl_xshelp.c b/tools/libxl/libxl_xshelp.c
index 4982b52..b3bac6d 100644
--- a/tools/libxl/libxl_xshelp.c
+++ b/tools/libxl/libxl_xshelp.c
@@ -20,8 +20,12 @@
 char **libxl__xs_kvs_of_flexarray(libxl__gc *gc, flexarray_t *array)
 {
     char **kvs;
-    int i, length = array->count;
+    int i, length;
 
+    if (!array)
+        return NULL;
+
+    length = array->count;
     if (!length)
         return NULL;
 
--
generated by git-patchbot for /home/xen/git/xen.git#master

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