[libvirt] [PATCH] migrate: v2: use VIR_DOMAIN_XML_MIGRATABLE when available

[Ján Tomko]

In v2 migration protocol, XML is obtained by calling domainGetXMLDesc.
This includes the default USB controller in XML, which breaks migration
to older libvirt (before 0.9.2).

Commit 409b5f549530e7b3a33f4505f2cad2e26896107c
    qemu: Emit compatible XML when migrating a domain
only fixed this for v3 migration.

This patch uses the new VIR_DOMAIN_XML_MIGRATABLE flag (detected by
VIR_DRV_FEATURE_XML_MIGRATABLE) to obtain XML without the default controller,
enabling backward v2 migration.
---
 src/libvirt.c          |   13 ++++++++++---
 src/libvirt_internal.h |    5 +++++
 src/qemu/qemu_driver.c |    1 +
 3 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/src/libvirt.c b/src/libvirt.c
index e3ddf27..f6f5b91 100644
--- a/src/libvirt.c
+++ b/src/libvirt.c
@@ -4620,6 +4620,7 @@ virDomainMigrateVersion2 (virDomainPtr domain,
     int cookielen = 0, ret;
     virDomainInfo info;
     virErrorPtr orig_err = NULL;
+    unsigned int getxml_flags = 0;
     int cancelled;
     VIR_DOMAIN_DEBUG(domain,
                      "dconn=%p, flags=%lx, dname=%s, uri=%s, bandwidth=%lu",
@@ -4646,9 +4647,15 @@ virDomainMigrateVersion2 (virDomainPtr domain,
         virDispatchError(domain->conn);
         return NULL;
     }
-    dom_xml = domain->conn->driver->domainGetXMLDesc(domain,
-                                                     VIR_DOMAIN_XML_SECURE |
-                                                     VIR_DOMAIN_XML_UPDATE_CPU);
+
+    if (VIR_DRV_SUPPORTS_FEATURE(domain->conn->driver, domain->conn,
+                                 VIR_DRV_FEATURE_XML_MIGRATABLE)) {
+        getxml_flags |= VIR_DOMAIN_XML_MIGRATABLE;
+    } else {
+        getxml_flags |= VIR_DOMAIN_XML_SECURE | VIR_DOMAIN_XML_UPDATE_CPU;
+    }
+
+    dom_xml = domain->conn->driver->domainGetXMLDesc(domain, getxml_flags);
     if (!dom_xml)
         return NULL;
 
diff --git a/src/libvirt_internal.h b/src/libvirt_internal.h
index 23e7153..71483e4 100644
--- a/src/libvirt_internal.h
+++ b/src/libvirt_internal.h
@@ -95,6 +95,11 @@ enum {
      * messages).
      */
     VIR_DRV_FEATURE_PROGRAM_KEEPALIVE = 10,
+
+    /*
+     * Support for VIR_DOMAIN_XML_MIGRATABLE flag in domainGetXMLDesc
+     */
+    VIR_DRV_FEATURE_XML_MIGRATABLE = 11,
 };
 
 
diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 76730c6..0c35dad 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -1130,6 +1130,7 @@ qemudSupportsFeature (virConnectPtr conn ATTRIBUTE_UNUSED, int feature)
     case VIR_DRV_FEATURE_MIGRATE_CHANGE_PROTECTION:
     case VIR_DRV_FEATURE_FD_PASSING:
     case VIR_DRV_FEATURE_TYPED_PARAM_STRING:
+    case VIR_DRV_FEATURE_XML_MIGRATABLE:
         return 1;
     default:
         return 0;
-- 
1.7.8.6