[libvirt] [PATCH v2 6/7] vz: support misc migration options

nshirokovskiy at virtuozzo.com nshirokovskiy at virtuozzo.com
Fri Jul 17 12:55:06 UTC 2015

From: Nikolay Shirokovskiy <nshirokovskiy at virtuozzo.com>

Migration API has a lot of options. This patch intention is to provide
support for those options that can be trivially supported and give
estimation for other options support in this commit message.

I. Supported.

1. VIR_MIGRATE_COMPRESSED. Means 'use compression when migration domain
memory'. It is supported but quite uncommon way: vz migration demands that this
option should be set. This is due to vz is hardcoded to moving VMs memory using
compression. So anyone who wants to migrate vz domain should set this option
thus declaring it knows it uses compression.

Why bother? May be just support this option and ignore if it is not set or
don't support at all as we can't change behaviour in this aspect.  Well I
believe that this option is, first, inherent to hypervisor implementation as
we have a task of moving domain memory to different place and, second, we have
a tradeoff here between cpu and network resources and some managment should
choose the stratery via this option. If we choose ignoring or unsupporting
implementation than this option has a too vague meaning. Let's go into more

First if we ignore situation where option is not set than we put user into
fallacy that vz hypervisor don't use compression and thus have lower cpu
usage. Second approach is to not support the option. The main reason not to
follow this way is that 'not supported and not set' is indistinguishable from
'supported and not set' and thus again fool the user.

2. VIR_MIGRATE_LIVE. Means 'reduce domain downtime by suspending it as lately
as possible' which technically means 'migrate as much domain memory as possible
before suspending'. Supported in same manner as VIR_MIGRATE_COMPRESSED as both
vz VMs and CTs are always migrated via live scheme.

One may be fooled by vz sdk flags of migration api: PVMT_HOT_MIGRATION(aka
live) and PVMT_WARM_MIGRATION(aka normal). Current implementation ignore these
flags and always use live migration.

together. Vz domain are alwasy persistent so we have to support demand option
this is done just by unsupporting it).

4. VIR_MIGRATE_PAUSED. Means 'don't resume domain on destination'. This is
trivially supported as we have a corresponding option in vz migration.

5. VIR_MIGRATE_OFFLINE. Means 'migrate only XML definition of a domain'. It is
a forcing option that is it is ignored if domain is running and must be set
to migrate stopped domain. Vz implemenation follows this unformal definition
with one exception: non-shared disks will be migrated too. This desicion is on
par with VIR_MIGRATE_NON_SHARED_DISK condideration(see last part of this

All that said the minimal command to migrate vz domain looks next:

migrate $DOMAIN $DESTINATION --live --persistent --compressed.

Not good. Say if you want to just migrate a domain without further
details you will get error messages until you add these options to
command line. I think there is a lack of notion 'default' behaviour
in all these aspects. If we have it we could just issue:


For vz this would give default compression for example, for qemu - default
no-compression. Then we could have flags --compressed and -no-compressed
and for vz the latter would give unsupported error.

II. Unsupported.

1. VIR_MIGRATE_UNSAFE. Vz disks are always have 'cache=none' set (this
is not reflected in current version of vz driver and will be fixed
soon). So we need not to support this option.

2. VIR_MIGRATE_CHANGE_PROTECTION. Unsupported as we have no appopriate
support from vz sdk. Although we have locks they are advisory and
cant help us.

3. VIR_MIGRATE_TUNNELLED. Means 'use libvirtd to libvirtd connection
to pass hypervisor migration traffic'. Unsupported as not among
vz hypervisor usecases.

4. Direct migration. Which is exposed via *toURI* interface with
VIR_MIGRATE_PEER2PEER flag unset. Means 'migrate without using
libvirtd on the other side'. To support it we should add authN
means to vz driver as mentioned in 'backbone patch' which looks

Without further discussion. They are just not usecases of vz hypevisor.

III. Undecided and thus unsupported.

6. VIR_MIGRATE_NON_SHARED_DISK. The meaning of this option is not clear to me.
Look, if qemu domain has a non-shared disk than it will refuse to migrate. But
after you specify this option it will refuse too. You need to create image file
for the disk on the destination side. Only after that you can migrate.
Unexpectedly existence of this file is enough to migrate without option too. In
this case you will get a domain on the destination with disk image unrelated to
source one and this is in case of live migration! Looks like a bug. Ok, imagine
this is fixed so that migration of non-shared disk is only possible with
actual coping disk to destination. What we get from this option? We get
that you have to specify this option if you want to migrate a domain with
non-shared disk like some forcing option. May be it is a good approach
but it is incompatible with vz. Vz don't demand any user awareness of
migration of non-shared disks. And this case incompatibility can not
be easily resolved as for 'compressed' option as this option depends on
classifying of shared/non-shared for disks which is done inside vz.
vz: implement misc migration options

Signed-off-by: Nikolay Shirokovskiy <nshirokovskiy at virtuozzo.com>
 src/vz/vz_driver.c |   90 ++++++++++++++++++++++++++++++++++++++++++++++++++--
 src/vz/vz_sdk.c    |    8 +++-
 src/vz/vz_sdk.h    |    3 +-
 3 files changed, 95 insertions(+), 6 deletions(-)

diff --git a/src/vz/vz_driver.c b/src/vz/vz_driver.c
index c6086a7..74bf516 100644
--- a/src/vz/vz_driver.c
+++ b/src/vz/vz_driver.c
@@ -1435,13 +1435,88 @@ vzParseVzURI(const char *uri_str)
     return uri;
+#define VZ_MIGRATION_FLAGS          \
+    (VIR_MIGRATE_PEER2PEER |        \
+     VIR_MIGRATE_OFFLINE |          \
+     VIR_MIGRATE_LIVE |             \
 #define VZ_MIGRATION_PARAMETERS                                 \
+/* TODO this code should be in common place as these
+   rules follows from options (informal) definitions.
+   Qemu makes some of these checks on begin phase but not all. */
+int vzCheckOfflineFlags(int flags)
+    if (!(flags & VIR_MIGRATE_OFFLINE)) {
+        virReportError(VIR_ERR_OPERATION_INVALID,
+                       "%s", _("domain is not running"));
+        return -1;
+    }
+    if (flags & VIR_MIGRATE_LIVE) {
+        virReportError(VIR_ERR_OPERATION_INVALID, "%s",
+                       _("live offline migration does not "
+                         "make sense"));
+        return -1;
+    }
+    if (flags & VIR_MIGRATE_COMPRESSED) {
+        virReportError(VIR_ERR_OPERATION_INVALID, "%s",
+                       _("compressed offline migration does not "
+                         "make sense"));
+        return -1;
+    }
+    if (flags & VIR_MIGRATE_PAUSED) {
+        virReportError(VIR_ERR_OPERATION_INVALID, "%s",
+                       _("paused offline migration does not "
+                         "make sense"));
+        return -1;
+    }
+    return 0;
+int vzCheckCommonFlags(int flags)
+    virCheckFlags(VZ_MIGRATION_FLAGS, -1);
+    if (!(flags & VIR_MIGRATE_PERSIST_DEST)) {
+        virReportError(VIR_ERR_INVALID_ARG, "%s",
+                            _("flags VIR_MIGRATE_PERSIST_DEST must be set"
+                              " for vz migration"));
+        return -1;
+    }
+    return 0;
+int vzCheckOnlineFlags(int flags)
+    if (!(flags & VIR_MIGRATE_LIVE)) {
+        virReportError(VIR_ERR_INVALID_ARG, "%s",
+                            _("flags VIR_MIGRATE_LIVE must be set"
+                              " for online vz migration"));
+        return -1;
+    }
+    if (!(flags & VIR_MIGRATE_COMPRESSED)) {
+        virReportError(VIR_ERR_INVALID_ARG, "%s",
+                            _("flags VIR_MIGRATE_COMPRESSED must be set"
+                              " for online vz migration"));
+        return -1;
+    }
+    return 0;
 static int
 vzDomainMigratePerform3Params(virDomainPtr domain,
                               const char *dconnuri,
@@ -1462,7 +1537,8 @@ vzDomainMigratePerform3Params(virDomainPtr domain,
     const char *dname = NULL;
     const char *miguri = NULL;
-    virCheckFlags(flags, -1);
+    if (vzCheckCommonFlags(flags))
+        goto cleanup;
     if (virTypedParamsValidate(params, nparams, VZ_MIGRATION_PARAMETERS) < 0)
         goto cleanup;
@@ -1484,6 +1560,14 @@ vzDomainMigratePerform3Params(virDomainPtr domain,
     if (!(dom = vzDomObjFromDomain(domain)))
         goto cleanup;
+    if (virDomainObjIsActive(dom))
+        ret = vzCheckOnlineFlags(flags);
+    else
+        ret = vzCheckOfflineFlags(flags);
+    if (ret < 0)
+        goto cleanup;
     dconn = virConnectOpen(dconnuri);
     if (dconn == NULL) {
@@ -1495,7 +1579,7 @@ vzDomainMigratePerform3Params(virDomainPtr domain,
     if (virConnectVzGetSessionUUID(dconn, session_uuid) < 0)
         goto cleanup;
-    if (prlsdkMigrate(dom, vzuri, session_uuid, dname) < 0)
+    if (prlsdkMigrate(dom, vzuri, session_uuid, dname, flags) < 0)
         goto cleanup;
     virDomainObjListRemove(privconn->domains, dom);
diff --git a/src/vz/vz_sdk.c b/src/vz/vz_sdk.c
index 89a2429..9a2b5df 100644
--- a/src/vz/vz_sdk.c
+++ b/src/vz/vz_sdk.c
@@ -4065,18 +4065,22 @@ prlsdkGetMemoryStats(virDomainObjPtr dom,
 int prlsdkMigrate(virDomainObjPtr dom, virURIPtr uri,
                   const unsigned char *session_uuid,
-                  const char *dname)
+                  const char *dname, unsigned int flags)
     int ret = -1;
     vzDomObjPtr privdom = dom->privateData;
     char uuidstr[VIR_UUID_STRING_BUFLEN + 2];
+    if (flags & VIR_MIGRATE_PAUSED)
+        vzflags |= PVMT_DONT_RESUME_VM;
     prlsdkUUIDFormat(session_uuid, uuidstr);
     job = PrlVm_MigrateWithRenameEx(privdom->sdkdom, uri->server, uri->port, uuidstr,
                                     dname == NULL ? "" : dname,
                                     "", /* use default dir for migrated instance bundle */
-                                    PRLSDK_MIGRATION_FLAGS,
+                                    vzflags,
                                     0, /* reserved flags */
                                     PRL_TRUE /* don't ask for confirmations */
diff --git a/src/vz/vz_sdk.h b/src/vz/vz_sdk.h
index 0aa70b3..5b26b70 100644
--- a/src/vz/vz_sdk.h
+++ b/src/vz/vz_sdk.h
@@ -80,4 +80,5 @@ int
 prlsdkMigrate(virDomainObjPtr dom,
               virURIPtr uri,
               const char unsigned *session_uuid,
-              const char *dname);
+              const char *dname,
+              unsigned int flags);

More information about the libvir-list mailing list