[Xen-devel] [PATCH 3 of 3] blktap3/libxl: Handles blktap3 device in libxl

[Thanos Makatos <thanos.makatos@xxxxxxxxxx>]

Handling of blktap3 devices is similar to blktap2, except that libxl doesn't
spawn the tapdisk and doesn't create the physical device in dom0.

diff -r dd63f2992e71 -r 6b54db4abe12 tools/libxl/libxl.c
--- a/tools/libxl/libxl.c       Fri Feb 08 17:23:25 2013 +0000
+++ b/tools/libxl/libxl.c       Fri Feb 08 17:23:26 2013 +0000
@@ -1158,6 +1158,8 @@ static void disk_eject_xswatch_callback(
         disk->backend = LIBXL_DISK_BACKEND_TAP;
     } else if (!strcmp(backend_type, "qdisk")) {
         disk->backend = LIBXL_DISK_BACKEND_QDISK;
+    } else if (!strcmp(backend_type, "tap3")) {
+        disk->backend = LIBXL_DISK_BACKEND_TAP3;
     } else {
         disk->backend = LIBXL_DISK_BACKEND_UNKNOWN;
     }
@@ -1998,6 +2000,9 @@ int libxl__device_from_disk(libxl__gc *g
         case LIBXL_DISK_BACKEND_QDISK:
             device->backend_kind = LIBXL__DEVICE_KIND_QDISK;
             break;
+        case LIBXL_DISK_BACKEND_TAP3:
+            device->backend_kind = LIBXL__DEVICE_KIND_VBD3;
+            break;
         default:
             LIBXL__LOG(ctx, LIBXL__LOG_ERROR, "unrecognized disk backend type: 
%d\n",
                        disk->backend);
@@ -2113,6 +2118,12 @@ static void device_disk_add(libxl__egc *
 
                 /* now create a phy device to export the device to the guest */
                 goto do_backend_phy;
+            case LIBXL_DISK_BACKEND_TAP3:
+                flexarray_append(back, "params");
+                flexarray_append(back, libxl__sprintf(gc, "%s:%s",
+                    libxl__device_disk_string_of_format(disk->format),
+                    disk->pdev_path));
+                break;
             case LIBXL_DISK_BACKEND_QDISK:
                 flexarray_append(back, "params");
                 flexarray_append(back, libxl__sprintf(gc, "%s:%s",
diff -r dd63f2992e71 -r 6b54db4abe12 tools/libxl/libxl_device.c
--- a/tools/libxl/libxl_device.c        Fri Feb 08 17:23:25 2013 +0000
+++ b/tools/libxl/libxl_device.c        Fri Feb 08 17:23:26 2013 +0000
@@ -190,6 +190,23 @@ static int disk_try_backend(disk_try_bac
         }
         return backend;
 
+    case LIBXL_DISK_BACKEND_TAP3:
+        /* TODO What's that script thing? */
+        if (a->disk->script) goto bad_script;
+
+        if (!libxl__blktap3_enabled(a->gc)) {
+            LIBXL__LOG(ctx, LIBXL__LOG_DEBUG, "Disk vdev=%s, backend tap"
+                       " unsuitable because blktap3 not available",
+                       a->disk->vdev);
+            return 0;
+        }
+        /* TODO other formats supported by blktap3? */
+        if (!(a->disk->format == LIBXL_DISK_FORMAT_RAW ||
+              a->disk->format == LIBXL_DISK_FORMAT_VHD)) {
+            goto bad_format;
+        }
+        return backend;
+
     case LIBXL_DISK_BACKEND_QDISK:
         if (a->disk->script) goto bad_script;
         return backend;
@@ -258,6 +275,7 @@ int libxl__device_disk_set_backend(libxl
         ok=
             disk_try_backend(&a, LIBXL_DISK_BACKEND_PHY) ?:
             disk_try_backend(&a, LIBXL_DISK_BACKEND_TAP) ?:
+            disk_try_backend(&a, LIBXL_DISK_BACKEND_TAP3) ?:
             disk_try_backend(&a, LIBXL_DISK_BACKEND_QDISK);
         if (ok)
             LIBXL__LOG(ctx, LIBXL__LOG_DEBUG, "Disk vdev=%s, using backend %s",
@@ -290,6 +308,7 @@ char *libxl__device_disk_string_of_backe
     switch (backend) {
         case LIBXL_DISK_BACKEND_QDISK: return "qdisk";
         case LIBXL_DISK_BACKEND_TAP: return "phy";
+        case LIBXL_DISK_BACKEND_TAP3: return "phy";
         case LIBXL_DISK_BACKEND_PHY: return "phy";
         default: return NULL;
     }

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