libxl: support Xen migration stream V2 in save/restore

Xen 4.6 introduced a new migration stream commonly referred to as
"migration V2". Xen 4.6 and newer always produce this new stream,
whereas Xen 4.5 and older always produce the legacy stream.
Support for migration stream V2 can be detected at build time with
LIBXL_HAVE_SRM_V2 from libxl.h. The legacy and V2 streams are not
compatible, but a V2 host can accept and convert a legacy stream.

Commit e7440656 changed the libxl driver to use the lowest libxl
API version possible (version 0x040200) to ensure the driver
builds against older Xen releases. The old 4.2 restore API does
not support specifying a stream version and assumes a legacy
stream, even if the incoming stream is migration V2. Thinking it
has been given a legacy stream, libxl will fail to convert an
incoming stream that is already V2, which causes the entire
restore operation to fail. Xen's libvirt-related OSSTest has been
failing since commit e7440656 landed in libvirt.git master. One
of the more recent failures can be seen here

http://lists.xenproject.org/archives/html/xen-devel/2016-05/msg00071.html

This patch changes the call to libxl_domain_create_restore() to
include the stream version if LIBXL_HAVE_SRM_V2 is defined. The
version field of the libxlSavefileHeader struct is also updated
to '2' when LIBXL_HAVE_SRM_V2 is defined, ensuring the stream
version in the header matches the actual stream version produced
by Xen. Along with bumping the libxl API requirement to 0x040400,
this patch fixes save/restore on a migration V2 Xen host.

Oddly, migration has never used the libxlSavefileHeader. It
handles passing configuration in the Begin and Prepare phases,
and then calls libxl directly to transfer domain state/memory
in the Perform phase. A subsequent patch will add stream
version handling in the Begin and Prepare phase handshaking,
which will fix the migration related OSSTest failures.

Signed-off-by: Jim Fehlig <jfehlig@suse.com>

diff --git a/src/libxl/libxl_conf.h b/src/libxl/libxl_conf.h
index 24e29116f2ef7b103ccb852262c3004a18a530e4..c5b94295ddb21f1c745b6aaaf0099e787fa42f2b 100644 (file)
--- a/src/libxl/libxl_conf.h
+++ b/src/libxl/libxl_conf.h
@@ -148,7 +148,11 @@ struct _libxlDriverPrivate {
 };
 
 # define LIBXL_SAVE_MAGIC "libvirt-xml\n \0 \r"
-# define LIBXL_SAVE_VERSION 1
+# ifdef LIBXL_HAVE_SRM_V2
+#  define LIBXL_SAVE_VERSION 2
+# else
+#  define LIBXL_SAVE_VERSION 1
+# endif
 
 typedef struct _libxlSavefileHeader libxlSavefileHeader;
 typedef libxlSavefileHeader *libxlSavefileHeaderPtr;

diff --git a/src/libxl/libxl_domain.c b/src/libxl/libxl_domain.c
index 32ad946d4844ea3bd1cc9707f2a141912763295f..5fa1bd9f189185ae8c101a6659fd2f350ef28f44 100644 (file)
--- a/src/libxl/libxl_domain.c
+++ b/src/libxl/libxl_domain.c
@@ -514,7 +514,7 @@ libxlDomainShutdownThread(void *opaque)
     }
     libxlDomainDestroyInternal(driver, vm);
     libxlDomainCleanup(driver, vm);
-    if (libxlDomainStart(driver, vm, false, -1) < 0) {
+    if (libxlDomainStartNew(driver, vm, false) < 0) {
         virErrorPtr err = virGetLastError();
         VIR_ERROR(_("Failed to restart VM '%s': %s"),
                   vm->def->name, err ? err->message : _("unknown error"));
@@ -1006,14 +1006,23 @@ libxlDomainCreateIfaceNames(virDomainDefPtr def, libxl_domain_config *d_config)
 }
 
 
+#ifdef LIBXL_HAVE_SRM_V2
+# define LIBXL_DOMSTART_RESTORE_VER_ATTR /* empty */
+#else
+# define LIBXL_DOMSTART_RESTORE_VER_ATTR ATTRIBUTE_UNUSED
+#endif
+
 /*
  * Start a domain through libxenlight.
  *
  * virDomainObjPtr must be locked and a job acquired on invocation
  */
-int
-libxlDomainStart(libxlDriverPrivatePtr driver, virDomainObjPtr vm,
-                 bool start_paused, int restore_fd)
+static int
+libxlDomainStart(libxlDriverPrivatePtr driver,
+                 virDomainObjPtr vm,
+                 bool start_paused,
+                 int restore_fd,
+                 uint32_t restore_ver LIBXL_DOMSTART_RESTORE_VER_ATTR)
 {
     libxl_domain_config d_config;
     virDomainDefPtr def = NULL;
@@ -1049,6 +1058,7 @@ libxlDomainStart(libxlDriverPrivatePtr driver, virDomainObjPtr vm,
                 goto cleanup;
 
             restore_fd = managed_save_fd;
+            restore_ver = hdr.version;
 
             if (STRNEQ(vm->def->name, def->name) ||
                 memcmp(vm->def->uuid, def->uuid, VIR_UUID_BUFLEN)) {
@@ -1117,6 +1127,9 @@ libxlDomainStart(libxlDriverPrivatePtr driver, virDomainObjPtr vm,
                                       &domid, NULL, &aop_console_how);
     } else {
         libxl_domain_restore_params_init(&params);
+#ifdef LIBXL_HAVE_SRM_V2
+        params.stream_version = restore_ver;
+#endif
         ret = libxl_domain_create_restore(cfg->ctx, &d_config, &domid,
                                           restore_fd, &params, NULL,
                                           &aop_console_how);
@@ -1203,6 +1216,25 @@ libxlDomainStart(libxlDriverPrivatePtr driver, virDomainObjPtr vm,
     return ret;
 }
 
+int
+libxlDomainStartNew(libxlDriverPrivatePtr driver,
+            virDomainObjPtr vm,
+            bool start_paused)
+{
+    return libxlDomainStart(driver, vm, start_paused, -1, LIBXL_SAVE_VERSION);
+}
+
+int
+libxlDomainStartRestore(libxlDriverPrivatePtr driver,
+                        virDomainObjPtr vm,
+                        bool start_paused,
+                        int restore_fd,
+                        uint32_t restore_ver)
+{
+    return libxlDomainStart(driver, vm, start_paused,
+                            restore_fd, restore_ver);
+}
+
 bool
 libxlDomainDefCheckABIStability(libxlDriverPrivatePtr driver,
                                 virDomainDefPtr src,

diff --git a/src/libxl/libxl_domain.h b/src/libxl/libxl_domain.h
index 1c1eba380008461872e56d7e59ff228efcc8065a..c53adaa1e29ef4f2ad931ccf1b2c791afd8d89eb 100644 (file)
--- a/src/libxl/libxl_domain.h
+++ b/src/libxl/libxl_domain.h
@@ -142,10 +142,16 @@ libxlDomainSetVcpuAffinities(libxlDriverPrivatePtr driver,
                              virDomainObjPtr vm);
 
 int
-libxlDomainStart(libxlDriverPrivatePtr driver,
-                 virDomainObjPtr vm,
-                 bool start_paused,
-                 int restore_fd);
+libxlDomainStartNew(libxlDriverPrivatePtr driver,
+                    virDomainObjPtr vm,
+                    bool start_paused);
+
+int
+libxlDomainStartRestore(libxlDriverPrivatePtr driver,
+                        virDomainObjPtr vm,
+                        bool start_paused,
+                        int restore_fd,
+                        uint32_t restore_ver);
 
 bool
 libxlDomainDefCheckABIStability(libxlDriverPrivatePtr driver,

diff --git a/src/libxl/libxl_driver.c b/src/libxl/libxl_driver.c
index bf97c9c1160796bf5c9aaf327abcef87fa3f130f..8977ae2cacc772e778d434ef94f46e2addb4b041 100644 (file)
--- a/src/libxl/libxl_driver.c
+++ b/src/libxl/libxl_driver.c
@@ -323,7 +323,7 @@ libxlAutostartDomain(virDomainObjPtr vm,
     }
 
     if (vm->autostart && !virDomainObjIsActive(vm) &&
-        libxlDomainStart(driver, vm, false, -1) < 0) {
+        libxlDomainStartNew(driver, vm, false) < 0) {
         err = virGetLastError();
         VIR_ERROR(_("Failed to autostart VM '%s': %s"),
                   vm->def->name,
@@ -998,8 +998,8 @@ libxlDomainCreateXML(virConnectPtr conn, const char *xml,
         goto cleanup;
     }
 
-    if (libxlDomainStart(driver, vm, (flags & VIR_DOMAIN_START_PAUSED) != 0,
-                     -1) < 0) {
+    if (libxlDomainStartNew(driver, vm,
+                         (flags & VIR_DOMAIN_START_PAUSED) != 0) < 0) {
         if (!vm->persistent) {
             virDomainObjListRemove(driver->domains, vm);
             vm = NULL;
@@ -1818,7 +1818,9 @@ libxlDomainRestoreFlags(virConnectPtr conn, const char *from,
         goto cleanup;
     }
 
-    ret = libxlDomainStart(driver, vm, (flags & VIR_DOMAIN_SAVE_PAUSED) != 0, fd);
+    ret = libxlDomainStartRestore(driver, vm,
+                                  (flags & VIR_DOMAIN_SAVE_PAUSED) != 0,
+                                  fd, hdr.version);
     if (ret < 0 && !vm->persistent)
         virDomainObjListRemove(driver->domains, vm);
 
@@ -2681,7 +2683,8 @@ libxlDomainCreateWithFlags(virDomainPtr dom,
         goto endjob;
     }
 
-    ret = libxlDomainStart(driver, vm, (flags & VIR_DOMAIN_START_PAUSED) != 0, -1);
+    ret = libxlDomainStartNew(driver, vm,
+                              (flags & VIR_DOMAIN_START_PAUSED) != 0);
     if (ret < 0)
         goto endjob;
     dom->id = vm->def->id;

diff --git a/src/libxl/libxl_migration.c b/src/libxl/libxl_migration.c
index ab1f76e32d6c53f4678489a1f8d58c9eb29220ad..1d4ec5ecf23bd94c0f2fae95f5a393af1713ac33 100644 (file)
--- a/src/libxl/libxl_migration.c
+++ b/src/libxl/libxl_migration.c
@@ -106,7 +106,7 @@ libxlDoMigrateReceive(void *opaque)
      * Always start the domain paused.  If needed, unpause in the
      * finish phase, after transfer of the domain is complete.
      */
-    ret = libxlDomainStart(driver, vm, true, recvfd);
+    ret = libxlDomainStartRestore(driver, vm, true, recvfd, LIBXL_SAVE_VERSION);
 
     if (ret < 0 && !vm->persistent)
         remove_dom = true;