[Xen-devel] [PATCH] libxl: do not start a xenpv qemu solely for tap devices if blktap is available

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

# HG changeset patch
# User Ian Campbell <ian.campbell@xxxxxxxxxx>
# Date 1300184217 0
# Node ID 1e18165335b02171ae1ff2ba426086004c34938c
# Parent  3b7471b486b5282138fbe202f996ea80230252b3
libxl: do not start a xenpv qemu solely for tap devices if blktap is available

qemu is used as a fallback for DISK_BACKEND_TAP if no blktap is
available but if blktap is available, or for DISK_BACKEND_PHY, we
don't need a qemu process.

Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>

diff -r 3b7471b486b5 -r 1e18165335b0 tools/libxl/libxl_dm.c
--- a/tools/libxl/libxl_dm.c    Tue Mar 15 10:07:09 2011 +0000
+++ b/tools/libxl/libxl_dm.c    Tue Mar 15 10:16:57 2011 +0000
@@ -840,8 +840,29 @@ int libxl__need_xenpv_qemu(libxl_ctx *ct
         goto out;
     }
 
-    if (nr_disks > 0 && !libxl__blktap_enabled(&gc))
-        ret = 1;
+    if (nr_disks > 0) {
+        int blktap_enabled = -1;
+        for (i = 0; i < nr_disks; i++) {
+            switch (disks[i].backend) {
+            case DISK_BACKEND_TAP:
+                if (blktap_enabled == -1)
+                    blktap_enabled = libxl__blktap_enabled(&gc);
+                if (!blktap_enabled) {
+                    ret = 1;
+                    goto out;
+                }
+                break;
+
+            case DISK_BACKEND_QDISK:
+                ret = 1;
+                goto out;
+
+            case DISK_BACKEND_PHY:
+            case DISK_BACKEND_UNKNOWN:
+                break;
+            }
+        }
+    }
 
 out:
     libxl__free_all(&gc);

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