libxl: Make sure devices added by pci-attach are reflected in the config

Currently libxl__device_pci_add_xenstore() is broken in that does not
update the domain's configuration for the first device added (which causes
creation of the overall backend area in xenstore). This can be easily observed
by running 'xl list -l' after adding a single device: the device will be
missing.

This patch fixes the problem and adds a DEBUG log line to allow easy
verification that the domain configuration is being modified. Also, the use
of libxl__device_generic_add() is dropped as it leads to a confusing situation
where only partial backend information is written under the xenstore
'/libxl' path. For LIBXL__DEVICE_KIND_PCI devices the only definitive
information in xenstore is under '/local/domain/0/backend' (the '0' being
hard-coded).

NOTE: This patch includes a whitespace in add_pcis_done().

Signed-off-by: Paul Durrant <pdurrant@amazon.com>
Reviewed-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Acked-by: Wei Liu <wl@xen.org>

tools/libs/light/libxl_pci.c

@@ -79,39 +79,55 @@ static void libxl__device_from_pci(libxl__gc *gc, uint32_t domid,
     device->kind = LIBXL__DEVICE_KIND_PCI;
 }
 
-static int libxl__create_pci_backend(libxl__gc *gc, uint32_t domid,
-                                     const libxl_device_pci *pci,
-                                     int num)
+static void libxl__create_pci_backend(libxl__gc *gc, xs_transaction_t t,
+                                      uint32_t domid, const libxl_device_pci *pci)
 {
-    flexarray_t *front = NULL;
-    flexarray_t *back = NULL;
-    libxl__device device;
-    int i;
+    libxl_ctx *ctx = libxl__gc_owner(gc);
+    flexarray_t *front, *back;
+    char *fe_path, *be_path;
+    struct xs_permissions fe_perms[2], be_perms[2];
+
+    LOGD(DEBUG, domid, "Creating pci backend");
 
     front = flexarray_make(gc, 16, 1);
     back = flexarray_make(gc, 16, 1);
 
-    LOGD(DEBUG, domid, "Creating pci backend");
-
-    /* add pci device */
-    libxl__device_from_pci(gc, domid, pci, &device);
+    fe_path = libxl__domain_device_frontend_path(gc, domid, 0,
+                                                 LIBXL__DEVICE_KIND_PCI);
+    be_path = libxl__domain_device_backend_path(gc, 0, domid, 0,
+                                                LIBXL__DEVICE_KIND_PCI);
 
+    flexarray_append_pair(back, "frontend", fe_path);
     flexarray_append_pair(back, "frontend-id", GCSPRINTF("%d", domid));
-    flexarray_append_pair(back, "online", "1");
+    flexarray_append_pair(back, "online", GCSPRINTF("%d", 1));
     flexarray_append_pair(back, "state", GCSPRINTF("%d", XenbusStateInitialising));
     flexarray_append_pair(back, "domain", libxl__domid_to_name(gc, domid));
 
-    for (i = 0; i < num; i++, pci++)
-        libxl_create_pci_backend_device(gc, back, i, pci);
+    be_perms[0].id = 0;
+    be_perms[0].perms = XS_PERM_NONE;
+    be_perms[1].id = domid;
+    be_perms[1].perms = XS_PERM_READ;
 
-    flexarray_append_pair(back, "num_devs", GCSPRINTF("%d", num));
+    xs_rm(ctx->xsh, t, be_path);
+    xs_mkdir(ctx->xsh, t, be_path);
+    xs_set_permissions(ctx->xsh, t, be_path, be_perms,
+                       ARRAY_SIZE(be_perms));
+    libxl__xs_writev(gc, t, be_path, libxl__xs_kvs_of_flexarray(gc, back));
+
+    flexarray_append_pair(front, "backend", be_path);
     flexarray_append_pair(front, "backend-id", GCSPRINTF("%d", 0));
     flexarray_append_pair(front, "state", GCSPRINTF("%d", XenbusStateInitialising));
 
-    return libxl__device_generic_add(gc, XBT_NULL, &device,
-                                     libxl__xs_kvs_of_flexarray(gc, back),
-                                     libxl__xs_kvs_of_flexarray(gc, front),
-                                     NULL);
+    fe_perms[0].id = domid;
+    fe_perms[0].perms = XS_PERM_NONE;
+    fe_perms[1].id = 0;
+    fe_perms[1].perms = XS_PERM_READ;
+
+    xs_rm(ctx->xsh, t, fe_path);
+    xs_mkdir(ctx->xsh, t, fe_path);
+    xs_set_permissions(ctx->xsh, t, fe_path,
+                       fe_perms, ARRAY_SIZE(fe_perms));
+    libxl__xs_writev(gc, t, fe_path, libxl__xs_kvs_of_flexarray(gc, front));
 }
 
 static int libxl__device_pci_add_xenstore(libxl__gc *gc,
@@ -135,8 +151,6 @@ static int libxl__device_pci_add_xenstore(libxl__gc *gc,
     be_path = libxl__domain_device_backend_path(gc, 0, domid, 0,
                                                 LIBXL__DEVICE_KIND_PCI);
     num_devs = libxl__xs_read(gc, XBT_NULL, GCSPRINTF("%s/num_devs", be_path));
-    if (!num_devs)
-        return libxl__create_pci_backend(gc, domid, pci, 1);
 
     libxl_domain_type domtype = libxl__domain_type(gc, domid);
     if (domtype == LIBXL_DOMAIN_TYPE_INVALID)
@@ -150,17 +164,17 @@ static int libxl__device_pci_add_xenstore(libxl__gc *gc,
     back = flexarray_make(gc, 16, 1);
 
     LOGD(DEBUG, domid, "Adding new pci device to xenstore");
-    num = atoi(num_devs);
+    num = num_devs ? atoi(num_devs) : 0;
     libxl_create_pci_backend_device(gc, back, num, pci);
     flexarray_append_pair(back, "num_devs", GCSPRINTF("%d", num + 1));
-    if (!starting)
+    if (num && !starting)
         flexarray_append_pair(back, "state", GCSPRINTF("%d", XenbusStateReconfiguring));
 
     /*
      * Stubdomin config is derived from its target domain, it doesn't have
      * its own file.
      */
-    if (!is_stubdomain) {
+    if (!is_stubdomain && !starting) {
         lock = libxl__lock_domain_userdata(gc, domid);
         if (!lock) {
             rc = ERROR_LOCK_FAIL;
@@ -170,6 +184,7 @@ static int libxl__device_pci_add_xenstore(libxl__gc *gc,
         rc = libxl__get_domain_configuration(gc, domid, &d_config);
         if (rc) goto out;
 
+        LOGD(DEBUG, domid, "Adding new pci device to config");
         device_add_domain_config(gc, &d_config, &libxl__pci_devtype,
                                  pci);
 
@@ -186,6 +201,10 @@ static int libxl__device_pci_add_xenstore(libxl__gc *gc,
             if (rc) goto out;
         }
 
+        /* This is the first device, so create the backend */
+        if (!num_devs)
+            libxl__create_pci_backend(gc, t, domid, pci);
+
         libxl__xs_writev(gc, t, be_path, libxl__xs_kvs_of_flexarray(gc, back));
 
         rc = libxl__xs_transaction_commit(gc, &t);
@@ -1437,7 +1456,7 @@ out_no_irq:
         }
     }
 
-    if (!starting && !libxl_get_stubdom_id(CTX, domid))
+    if (!libxl_get_stubdom_id(CTX, domid))
         rc = libxl__device_pci_add_xenstore(gc, domid, pci, starting);
     else
         rc = 0;
@@ -1765,28 +1784,12 @@ static void libxl__add_pcis(libxl__egc *egc, libxl__ao *ao, uint32_t domid,
 }
 
 static void add_pcis_done(libxl__egc *egc, libxl__multidev *multidev,
-                             int rc)
+                          int rc)
 {
     EGC_GC;
     add_pcis_state *apds = CONTAINER_OF(multidev, *apds, multidev);
-
-    /* Convenience aliases */
-    libxl_domain_config *d_config = apds->d_config;
-    libxl_domid domid = apds->domid;
     libxl__ao_device *aodev = apds->outer_aodev;
 
-    if (rc) goto out;
-
-    if (d_config->num_pcidevs > 0 && !libxl_get_stubdom_id(CTX, domid)) {
-        rc = libxl__create_pci_backend(gc, domid, d_config->pcidevs,
-                                       d_config->num_pcidevs);
-        if (rc < 0) {
-            LOGD(ERROR, domid, "libxl_create_pci_backend failed: %d", rc);
-            goto out;
-        }
-    }
-
-out:
     aodev->rc = rc;
     aodev->callback(egc, aodev);
 }