libxl: Allow multiple USB devices on HVM domain creation

This patch allows an HVM domain to be created with multiple USB
devices.

Since the previous interface only allowed the passing of a single
device, this requires us to add a new element to the hvm struct of
libxl_domain_build_info -- usbdevice_list.  For API compatibility, the
old element, usbdevice, remains.

If hvm.usbdevice_list is set, each device listed will cause an extra
"-usbdevice [foo]" to be appended to the qemu command line.

Callers may set either hvm.usbdevice or hvm.usbdevice_list, but not
both; libxl will throw an error if both are set.

In order to allow users of libxl to write software compatible with
older versions of libxl, also define LIBXL_HAVE_BUILDINFO_USBDEVICE_LIST.
If this is defined, callers may use either hvm.usbdevice or
hvm.usbdevice_list; otherwise, only hvm.usbdevice will be available.

as applied:
 - Fix whitespace errors -iwj
v3:
 - Duplicate functionality in both "new" and "old", since we're not
   unifying the two anymore.
v2:
 - Throw an error if both usbdevice and usbdevice_list are set
 - Update and clarify definition based on feedback
 - Previous patches means this works for both traditional and upstream

Signed-off-by: George Dunlap <george.dunlap@eu.citrix.com>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>

3 files changed, 53 insertions, 2 deletions

diff --git a/tools/libxl/libxl.h b/tools/libxl/libxl.h
index 030aa86d52..d18d22c0c1 100644
--- a/tools/libxl/libxl.h
+++ b/tools/libxl/libxl.h
@@ -273,6 +273,22 @@
 #endif
 #endif
 
+/*
+ * LIBXL_HAVE_BUILDINFO_USBDEVICE_LIST
+ *
+ * If this is defined, then the libxl_domain_build_info structure will
+ * contain hvm.usbdevice_list, a libxl_string_list type that contains
+ * a list of USB devices to specify on the qemu command-line.
+ *
+ * If it is set, callers may use either hvm.usbdevice or
+ * hvm.usbdevice_list, but not both; if both are set, libxl will
+ * throw an error.
+ *
+ * If this is not defined, callers can only use hvm.usbdevice.  Note
+ * that this means only one device can be added at domain build time.
+ */
+#define LIBXL_HAVE_BUILDINFO_USBDEVICE_LIST 1
+
 /* Functions annotated with LIBXL_EXTERNAL_CALLERS_ONLY may not be
  * called from within libxl itself. Callers outside libxl, who
  * do not #include libxl_internal.h, are fine. */
diff --git a/tools/libxl/libxl_dm.c b/tools/libxl/libxl_dm.c
index 82e30df6be..d10a58fc02 100644
--- a/tools/libxl/libxl_dm.c
+++ b/tools/libxl/libxl_dm.c
@@ -198,11 +198,28 @@ static char ** libxl__build_device_model_args_old(libxl__gc *gc,
         if (b_info->u.hvm.boot) {
             flexarray_vappend(dm_args, "-boot", b_info->u.hvm.boot, NULL);
         }
-        if (libxl_defbool_val(b_info->u.hvm.usb) || b_info->u.hvm.usbdevice) {
+        if (libxl_defbool_val(b_info->u.hvm.usb)
+            || b_info->u.hvm.usbdevice
+            || b_info->u.hvm.usbdevice_list) {
+            if ( b_info->u.hvm.usbdevice && b_info->u.hvm.usbdevice_list )
+            {
+                LOG(ERROR, "%s: Both usbdevice and usbdevice_list set",
+                    __func__);
+                return NULL;
+            }
             flexarray_append(dm_args, "-usb");
             if (b_info->u.hvm.usbdevice) {
                 flexarray_vappend(dm_args,
                                   "-usbdevice", b_info->u.hvm.usbdevice, NULL);
+            } else if (b_info->u.hvm.usbdevice_list) {
+                char **p;
+                for (p = b_info->u.hvm.usbdevice_list;
+                     *p;
+                     p++) {
+                    flexarray_vappend(dm_args,
+                                      "-usbdevice",
+                                      *p, NULL);
+                }
             }
         }
         if (b_info->u.hvm.soundhw) {
@@ -479,11 +496,28 @@ static char ** libxl__build_device_model_args_new(libxl__gc *gc,
             flexarray_vappend(dm_args, "-boot",
                     libxl__sprintf(gc, "order=%s", b_info->u.hvm.boot), NULL);
         }
-        if (libxl_defbool_val(b_info->u.hvm.usb) || b_info->u.hvm.usbdevice) {
+        if (libxl_defbool_val(b_info->u.hvm.usb)
+            || b_info->u.hvm.usbdevice
+            || b_info->u.hvm.usbdevice_list) {
+            if ( b_info->u.hvm.usbdevice && b_info->u.hvm.usbdevice_list )
+            {
+                LOG(ERROR, "%s: Both usbdevice and usbdevice_list set",
+                    __func__);
+                return NULL;
+            }
             flexarray_append(dm_args, "-usb");
             if (b_info->u.hvm.usbdevice) {
                 flexarray_vappend(dm_args,
                                   "-usbdevice", b_info->u.hvm.usbdevice, NULL);
+            } else if (b_info->u.hvm.usbdevice_list) {
+                char **p;
+                for (p = b_info->u.hvm.usbdevice_list;
+                     *p;
+                     p++) {
+                    flexarray_vappend(dm_args,
+                                      "-usbdevice",
+                                      *p, NULL);
+                }
             }
         }
         if (b_info->u.hvm.soundhw) {
diff --git a/tools/libxl/libxl_types.idl b/tools/libxl/libxl_types.idl
index f3c212bc8c..6cb6de613c 100644
--- a/tools/libxl/libxl_types.idl
+++ b/tools/libxl/libxl_types.idl
@@ -330,6 +330,7 @@ libxl_domain_build_info = Struct("domain_build_info",[
                                        ("usbdevice",        string),
                                        ("soundhw",          string),
                                        ("xen_platform_pci", libxl_defbool),
+                                       ("usbdevice_list",   libxl_string_list),
                                        ])),
                  ("pv", Struct(None, [("kernel", string),
                                       ("slack_memkb", MemKB),