Instead of a ternary operator we can use the existing helper. Signed-off-by: Peter Krempa <pkrempa(a)redhat.com&gt; --- src/qemu/qemu_monitor_json.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/src/qemu/qemu_monitor_json.c b/src/qemu/qemu_monitor_json.c index 1ecb06895c..4b339db399 100644 --- a/src/qemu/qemu_monitor_json.c +++ b/src/qemu/qemu_monitor_json.c @@ -574,7 +574,7 @@ static void qemuMonitorJSONHandleShutdown(qemuMonitor *mon, virJSONValue *data) virTristateBool guest_initiated = VIR_TRISTATE_BOOL_ABSENT; if (data && virJSONValueObjectGetBoolean(data, "guest", &guest) == 0) - guest_initiated = guest ? VIR_TRISTATE_BOOL_YES : VIR_TRISTATE_BOOL_NO; + guest_initiated = virTristateBoolFromBool(guest); qemuMonitorEmitShutdown(mon, guest_initiated); } -- 2.31.1

The migration API takes specific flags which are then converted to boolean parameters for the command. Extract the flag into helper variables rather than using ternary operatirs while constructing the command itself. Signed-off-by: Peter Krempa <pkrempa(a)redhat.com&gt; --- src/qemu/qemu_monitor_json.c | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-) diff --git a/src/qemu/qemu_monitor_json.c b/src/qemu/qemu_monitor_json.c index da14eee964..82631e30e0 100644 --- a/src/qemu/qemu_monitor_json.c +++ b/src/qemu/qemu_monitor_json.c @@ -3440,13 +3440,15 @@ int qemuMonitorJSONMigrate(qemuMonitor *mon, unsigned int flags, const char *uri) { - g_autoptr(virJSONValue) cmd = - qemuMonitorJSONMakeCommand("migrate", - "b:detach", flags & QEMU_MONITOR_MIGRATE_BACKGROUND ? 1 : 0, - "b:blk", flags & QEMU_MONITOR_MIGRATE_NON_SHARED_DISK ? 1 : 0, - "b:inc", flags & QEMU_MONITOR_MIGRATE_NON_SHARED_INC ? 1 : 0, - "s:uri", uri, - NULL); + bool detach = !!(flags & QEMU_MONITOR_MIGRATE_BACKGROUND); + bool blk = !!(flags & QEMU_MONITOR_MIGRATE_NON_SHARED_DISK); + bool inc = !!(flags & QEMU_MONITOR_MIGRATE_NON_SHARED_INC); + g_autoptr(virJSONValue) cmd = qemuMonitorJSONMakeCommand("migrate", + "b:detach", detach, + "b:blk", blk, + "b:inc", inc, + "s:uri", uri, + NULL); g_autoptr(virJSONValue) reply = NULL; if (!cmd) -- 2.31.1

Move the construction of the command from the variable declaration so that it doesn't exceed the line length and we can also move the logic of determining the protocol outside of the command construction. Signed-off-by: Peter Krempa <pkrempa(a)redhat.com&gt; --- src/qemu/qemu_monitor_json.c | 21 ++++++++++++--------- 1 file changed, 12 insertions(+), 9 deletions(-) diff --git a/src/qemu/qemu_monitor_json.c b/src/qemu/qemu_monitor_json.c index 82631e30e0..7cb6795a58 100644 --- a/src/qemu/qemu_monitor_json.c +++ b/src/qemu/qemu_monitor_json.c @@ -3590,17 +3590,20 @@ int qemuMonitorJSONGraphicsRelocate(qemuMonitor *mon, int tlsPort, const char *tlsSubject) { - g_autoptr(virJSONValue) cmd = qemuMonitorJSONMakeCommand("client_migrate_info", - "s:protocol", - (type == VIR_DOMAIN_GRAPHICS_TYPE_SPICE ? "spice" : "vnc"), - "s:hostname", hostname, - "i:port", port, - "i:tls-port", tlsPort, - "S:cert-subject", tlsSubject, - NULL); + const char *protocol = "vnc"; + g_autoptr(virJSONValue) cmd = NULL; g_autoptr(virJSONValue) reply = NULL; - if (!cmd) + if (type == VIR_DOMAIN_GRAPHICS_TYPE_SPICE) + protocol = "spice"; + + if (!(cmd = qemuMonitorJSONMakeCommand("client_migrate_info", + "s:protocol", protocol, + "s:hostname", hostname, + "i:port", port, + "i:tls-port", tlsPort, + "S:cert-subject", tlsSubject, + NULL))) return -1; if (qemuMonitorJSONCommand(mon, cmd, &reply) < 0) -- 2.31.1

Switch to the comment style allowing more text. Signed-off-by: Peter Krempa <pkrempa(a)redhat.com&gt; --- include/libvirt/libvirt-domain.h | 15 ++++++++------- 1 file changed, 8 insertions(+), 7 deletions(-) diff --git a/include/libvirt/libvirt-domain.h b/include/libvirt/libvirt-domain.h index 2f017c5b68..dddcae86a4 100644 --- a/include/libvirt/libvirt-domain.h +++ b/include/libvirt/libvirt-domain.h @@ -2590,13 +2590,14 @@ int virDomainBlockRebase(virDomainPtr dom, const char *disk, * Flags available for virDomainBlockCopy(). */ typedef enum { - VIR_DOMAIN_BLOCK_COPY_SHALLOW = 1 << 0, /* Limit copy to top of source - backing chain */ - VIR_DOMAIN_BLOCK_COPY_REUSE_EXT = 1 << 1, /* Reuse existing external - file for a copy */ - VIR_DOMAIN_BLOCK_COPY_TRANSIENT_JOB = 1 << 2, /* Don't force usage of - recoverable job for the - copy operation */ + /* Limit copy to top of source backing chain */ + VIR_DOMAIN_BLOCK_COPY_SHALLOW = 1 << 0, + + /* Reuse existing external file for a copy */ + VIR_DOMAIN_BLOCK_COPY_REUSE_EXT = 1 << 1, + + /* Don't force usage of recoverable job for the copy operation */ + VIR_DOMAIN_BLOCK_COPY_TRANSIENT_JOB = 1 << 2, } virDomainBlockCopyFlags; /** -- 2.31.1

Wire up the flag to enable the 'write-blocking' 'copy-mode' of 'blockdev-mirror'. It's not supported by all qemu versions but it is with those which we use -blockdev with so we can use that instead of adding another custom capability as we use blockdev for some time now. Signed-off-by: Peter Krempa <pkrempa(a)redhat.com&gt; --- src/qemu/qemu_driver.c | 16 +++++++++++++--- 1 file changed, 13 insertions(+), 3 deletions(-) diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c index 4cc1d20b89..a9fb840628 100644 --- a/src/qemu/qemu_driver.c +++ b/src/qemu/qemu_driver.c @@ -14902,12 +14902,14 @@ qemuDomainBlockCopyCommon(virDomainObj *vm, virStorageSource *n; virStorageSource *mirrorBacking = NULL; g_autoptr(GHashTable) blockNamedNodeData = NULL; + bool syncWrites = !!(flags & VIR_DOMAIN_BLOCK_COPY_SYNCHRONOUS_WRITES); int rc = 0; /* Preliminaries: find the disk we are editing, sanity checks */ virCheckFlags(VIR_DOMAIN_BLOCK_COPY_SHALLOW | VIR_DOMAIN_BLOCK_COPY_REUSE_EXT | - VIR_DOMAIN_BLOCK_COPY_TRANSIENT_JOB, -1); + VIR_DOMAIN_BLOCK_COPY_TRANSIENT_JOB | + VIR_DOMAIN_BLOCK_COPY_SYNCHRONOUS_WRITES, -1); if (virStorageSourceIsRelative(mirror)) { virReportError(VIR_ERR_INVALID_ARG, "%s", @@ -14945,6 +14947,12 @@ qemuDomainBlockCopyCommon(virDomainObj *vm, virDomainDiskDefSourceLUNValidate(mirror) < 0) goto endjob; + if (syncWrites && !blockdev) { + virReportError(VIR_ERR_OPERATION_UNSUPPORTED, "%s", + _("VIR_DOMAIN_BLOCK_COPY_SYNCHRONOUS_WRITES is not supported by this VM")); + goto endjob; + } + if (!(flags & VIR_DOMAIN_BLOCK_COPY_TRANSIENT_JOB) && vm->persistent) { /* XXX if qemu ever lets us start a new domain with mirroring @@ -15151,7 +15159,7 @@ qemuDomainBlockCopyCommon(virDomainObj *vm, qemuDomainDiskGetTopNodename(disk), mirror->nodeformat, bandwidth, granularity, buf_size, mirror_shallow, - false); + syncWrites); } else { /* qemuMonitorDriveMirror needs to honor the REUSE_EXT flag as specified * by the user */ @@ -15286,7 +15294,9 @@ qemuDomainBlockCopy(virDomainPtr dom, const char *disk, const char *destxml, virCheckFlags(VIR_DOMAIN_BLOCK_COPY_SHALLOW | VIR_DOMAIN_BLOCK_COPY_REUSE_EXT | - VIR_DOMAIN_BLOCK_COPY_TRANSIENT_JOB, -1); + VIR_DOMAIN_BLOCK_COPY_TRANSIENT_JOB | + VIR_DOMAIN_BLOCK_COPY_SYNCHRONOUS_WRITES, -1); + if (virTypedParamsValidate(params, nparams, VIR_DOMAIN_BLOCK_COPY_BANDWIDTH, VIR_TYPED_PARAM_ULLONG, -- 2.31.1

Separate the paragragraphs where the topic changes to simplify further additions. Signed-off-by: Peter Krempa <pkrempa(a)redhat.com&gt; --- docs/manpages/virsh.rst | 32 ++++++++++++++++++++------------ 1 file changed, 20 insertions(+), 12 deletions(-) diff --git a/docs/manpages/virsh.rst b/docs/manpages/virsh.rst index 9728f36a78..7c50388216 100644 --- a/docs/manpages/virsh.rst +++ b/docs/manpages/virsh.rst @@ -3187,9 +3187,12 @@ for peer-2-peer migration; *--direct* for direct migration; or *--tunnelled* for tunnelled migration. *--offline* migrates domain definition without starting the domain on destination and without stopping it on source host. Offline migration may be used with inactive domains and it must be used with -*--persistent* option. *--persistent* leaves the domain persistent on -destination host, *--undefinesource* undefines the domain on the source host, -and *--suspend* leaves the domain paused on the destination host. +*--persistent* option. + +*--persistent* leaves the domain persistent on destination host, +*--undefinesource* undefines the domain on the source host, and *--suspend* +leaves the domain paused on the destination host. + *--copy-storage-all* indicates migration with non-shared storage with full disk copy, *--copy-storage-inc* indicates migration with non-shared storage with incremental copy (same base image shared between source and destination). @@ -3198,15 +3201,20 @@ In both cases the disk images have to exist on destination host, the images on source host to the images found at the same place on the destination host. By default only non-shared non-readonly images are transferred. Use *--migrate-disks* to explicitly specify a list of disk targets to -transfer via the comma separated ``disk-list`` argument. *--change-protection* -enforces that no incompatible configuration changes will be made to the domain -while the migration is underway; this flag is implicitly enabled when supported -by the hypervisor, but can be explicitly used to reject the migration if the -hypervisor lacks change protection support. *--verbose* displays the progress -of migration. *--abort-on-error* cancels -the migration if a soft error (for example I/O error) happens during the -migration. *--postcopy* enables post-copy logic in migration, but does not -actually start post-copy, i.e., migration is started in pre-copy mode. +transfer via the comma separated ``disk-list`` argument. + +*--change-protection* enforces that no incompatible configuration changes will +be made to the domain while the migration is underway; this flag is implicitly +enabled when supported by the hypervisor, but can be explicitly used to reject +the migration if the hypervisor lacks change protection support. + +*--verbose* displays the progress of migration. + +*--abort-on-error* cancels the migration if a soft error (for example I/O error) +happens during the migration. + +*--postcopy* enables post-copy logic in migration, but does not actually start +post-copy, i.e., migration is started in pre-copy mode. Once migration is running, the user may switch to post-copy using the ``migrate-postcopy`` command sent from another virsh instance or use *--postcopy-after-precopy* along with *--postcopy* to let libvirt -- 2.31.1

Make the macro useful also for cases when one of multiple flags is required. Signed-off-by: Peter Krempa <pkrempa(a)redhat.com&gt; --- src/internal.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/src/internal.h b/src/internal.h index 2e404cd705..b6e4332542 100644 --- a/src/internal.h +++ b/src/internal.h @@ -374,7 +374,7 @@ */ #define VIR_REQUIRE_FLAG_RET(FLAG1, FLAG2, RET) \ do { \ - if ((flags & FLAG1) && !(flags & FLAG2)) { \ + if ((flags & (FLAG1)) && !(flags & (FLAG2))) { \ virReportInvalidArg(ctl, \ _("Flag '%s' is required by flag '%s'"), \ #FLAG2, #FLAG1); \ @@ -396,7 +396,7 @@ */ #define VIR_REQUIRE_FLAG_GOTO(FLAG1, FLAG2, LABEL) \ do { \ - if ((flags & FLAG1) && !(flags & FLAG2)) { \ + if ((flags & (FLAG1)) && !(flags & (FLAG2))) { \ virReportInvalidArg(ctl, \ _("Flag '%s' is required by flag '%s'"), \ #FLAG2, #FLAG1); \ -- 2.31.1

On a Friday in 2021, Peter Krempa wrote: synchronously converges Jano

After conversion the table doesn't have to custom colors, but otherwise seems to hold well. Signed-off-by: Peter Krempa <pkrempa(a)redhat.com&gt; --- docs/meson.build | 2 +- docs/migration.html.in | 688 ----------------------------------------- docs/migration.rst | 458 +++++++++++++++++++++++++++ 3 files changed, 459 insertions(+), 689 deletions(-) delete mode 100644 docs/migration.html.in create mode 100644 docs/migration.rst diff --git a/docs/meson.build b/docs/meson.build index fb6e0029d0..3aabb52950 100644 --- a/docs/meson.build +++ b/docs/meson.build @@ -77,7 +77,6 @@ docs_html_in_files = [ 'internals', 'java', 'logging', - 'migration', 'nss', 'pci-hotplug', 'php', @@ -121,6 +120,7 @@ docs_rst_files = [ 'hacking', 'libvirt-go', 'libvirt-go-xml', + 'migration', 'newreposetup', 'pci-addresses', 'platforms', diff --git a/docs/migration.html.in b/docs/migration.html.in deleted file mode 100644 index 627200f96a..0000000000 --- a/docs/migration.html.in +++ /dev/null @@ -1,688 +0,0 @@ -<?xml version="1.0" encoding="UTF-8"?> -<!DOCTYPE html> -<html xmlns="http://www.w3.org/1999/xhtml"> - <body> - <h1>Guest migration</h1> - - <ul id="toc"></ul> - - <p> - Migration of guests between hosts is a complicated problem with many possible - solutions, each with their own positive and negative points. For maximum - flexibility of both hypervisor integration, and administrator deployment, - libvirt implements several options for migration. - </p> - - <h2><a id="transport">Network data transports</a></h2> - - <p> - There are two options for the data transport used during migration, either - the hypervisor's own <strong>native</strong> transport, or <strong>tunnelled</strong> - over a libvirtd connection. - </p> - - <h3><a id="transportnative">Hypervisor native transport</a></h3> - <p> - <em>Native</em> data transports may or may not support encryption, depending - on the hypervisor in question, but will typically have the lowest computational costs - by minimising the number of data copies involved. The native data transports will also - require extra hypervisor-specific network configuration steps by the administrator when - deploying a host. For some hypervisors, it might be necessary to open up a large range - of ports on the firewall to allow multiple concurrent migration operations. - </p> - - <p> - Modern hypervisors support TLS for encryption and authentication of the - migration connections which can be enabled using the - <code>VIR_MIGRATE_TLS</code> flag. The <em>qemu</em> hypervisor driver - allows users to force use of TLS via the <code>migrate_tls_force</code> - knob configured in <code>/etc/libvirt/qemu.conf</code>. - </p> - - <p> - <img class="diagram" src="migration-native.png" alt="Migration native path"/> - </p> - - <h3><a id="transporttunnel">libvirt tunnelled transport</a></h3> - <p> - <em>Tunnelled</em> data transports will always be capable of strong encryption - since they are able to leverage the capabilities built in to the libvirt RPC protocol. - The downside of a tunnelled transport, however, is that there will be extra data copies - involved on both the source and destinations hosts as the data is moved between libvirtd - and the hypervisor. This is likely to be a more significant problem for guests with - very large RAM sizes, which dirty memory pages quickly. On the deployment side, tunnelled - transports do not require any extra network configuration over and above what's already - required for general libvirtd <a href="remote.html">remote access</a>, and there is only - need for a single port to be open on the firewall to support multiple concurrent - migration operations. - </p> - - <p> - <em>Note:</em> Certain features such as migration of non-shared storage - (<code>VIR_MIGRATE_NON_SHARED_DISK</code>), the multi-connection migration - (<code>VIR_MIGRATE_PARALLEL</code>), or post-copy migration - (<code>VIR_MIGRATE_POSTCOPY</code>) may not be available when using - libvirt's tunnelling. - </p> - - <p> - <img class="diagram" src="migration-tunnel.png" alt="Migration tunnel path"/> - </p> - - <h2><a id="flow">Communication control paths/flows</a></h2> - - <p> - Migration of virtual machines requires close co-ordination of the two - hosts involved, as well as the application invoking the migration, - which may be on the source, the destination, or a third host. - </p> - - <h3><a id="flowmanageddirect">Managed direct migration</a></h3> - - <p> - With <em>managed direct</em> migration, the libvirt client process - controls the various phases of migration. The client application must - be able to connect and authenticate with the libvirtd daemons on both - the source and destination hosts. There is no need for the two libvirtd - daemons to communicate with each other. If the client application - crashes, or otherwise loses its connection to libvirtd during the - migration process, an attempt will be made to abort the migration and - restart the guest CPUs on the source host. There may be scenarios - where this cannot be safely done, in which cases the guest will be - left paused on one or both of the hosts. - </p> - - <p> - <img class="diagram" src="migration-managed-direct.png" alt="Migration direct, managed"/> - </p> - - - <h3><a id="flowpeer2peer">Managed peer to peer migration</a></h3> - - <p> - With <em>peer to peer</em> migration, the libvirt client process only - talks to the libvirtd daemon on the source host. The source libvirtd - daemon controls the entire migration process itself, by directly - connecting the destination host libvirtd. If the client application crashes, - or otherwise loses its connection to libvirtd, the migration process - will continue uninterrupted until completion. Note that the - source libvirtd uses its own credentials (typically root) to - connect to the destination, rather than the credentials used - by the client to connect to the source; if these differ, it is - common to run into a situation where a client can connect to the - destination directly but the source cannot make the connection to - set up the peer-to-peer migration. - </p> - - <p> - <img class="diagram" src="migration-managed-p2p.png" alt="Migration peer-to-peer"/> - </p> - - - <h3><a id="flowunmanageddirect">Unmanaged direct migration</a></h3> - - <p> - With <em>unmanaged direct</em> migration, neither the libvirt client - or libvirtd daemon control the migration process. Control is instead - delegated to the hypervisor's over management services (if any). The - libvirt client merely initiates the migration via the hypervisor's - management layer. If the libvirt client or libvirtd crash, the - migration process will continue uninterrupted until completion. - </p> - - <p> - <img class="diagram" src="migration-unmanaged-direct.png" alt="Migration direct, unmanaged"/> - </p> - - - <h2><a id="security">Data security</a></h2> - - <p> - Since the migration data stream includes a complete copy of the guest - OS RAM, snooping of the migration data stream may allow compromise - of sensitive guest information. If the virtualization hosts have - multiple network interfaces, or if the network switches support - tagged VLANs, then it is very desirable to separate guest network - traffic from migration or management traffic. - </p> - - <p> - In some scenarios, even a separate network for migration data may - not offer sufficient security. In this case it is possible to apply - encryption to the migration data stream. If the hypervisor does not - itself offer encryption, then the libvirt tunnelled migration - facility should be used. - </p> - - <h2><a id="offline">Offline migration</a></h2> - - <p> - Offline migration transfers the inactive definition of a domain - (which may or may not be active). After successful completion, the - domain remains in its current state on the source host and is defined - but inactive on the destination host. It's a bit more clever than - <code>virsh dumpxml</code> on source host followed by - <code>virsh define</code> on destination host, as offline migration - will run the pre-migration hook to update the domain XML on - destination host. Currently, copying non-shared storage or other file - based storages (e.g. UEFI variable storage) is not supported during - offline migration. - </p> - - <h2><a id="uris">Migration URIs</a></h2> - - <p> - Initiating a guest migration requires the client application to - specify up to three URIs, depending on the choice of control - flow and/or APIs used. The first URI is that of the libvirt - connection to the source host, where the virtual guest is - currently running. The second URI is that of the libvirt - connection to the destination host, where the virtual guest - will be moved to (and in peer-to-peer migrations, this is from - the perspective of the source, not the client). The third URI is - a hypervisor specific - URI used to control how the guest will be migrated. With - any managed migration flow, the first and second URIs are - compulsory, while the third URI is optional. With the - unmanaged direct migration mode, the first and third URIs are - compulsory and the second URI is not used. - </p> - - <p> - Ordinarily management applications only need to care about the - first and second URIs, which are both in the normal libvirt - connection URI format. Libvirt will then automatically determine - the hypervisor specific URI, by looking up the target host's - configured hostname. There are a few scenarios where the management - application may wish to have direct control over the third URI. - </p> - - <ol> - <li>The configured hostname is incorrect, or DNS is broken. If a - host has a hostname which will not resolve to match one of its - public IP addresses, then libvirt will generate an incorrect - URI. In this case the management application should specify the - hypervisor specific URI explicitly, using an IP address, or a - correct hostname.</li> - <li>The host has multiple network interfaces. If a host has multiple - network interfaces, it might be desirable for the migration data - stream to be sent over a specific interface for either security - or performance reasons. In this case the management application - should specify the hypervisor specific URI, using an IP address - associated with the network to be used.</li> - <li>The firewall restricts what ports are available. When libvirt - generates a migration URI it will pick a port number using hypervisor - specific rules. Some hypervisors only require a single port to be - open in the firewalls, while others require a whole range of port - numbers. In the latter case the management application may wish - to choose a specific port number outside the default range in order - to comply with local firewall policies.</li> - <li>The second URI uses UNIX transport method. In this advanced case - libvirt should not guess a *migrateuri* and it should be specified using - UNIX socket path URI: <code>unix:///path/to/socket</code>.</li> - </ol> - - <h2><a id="config">Configuration file handling</a></h2> - - <p> - There are two types of virtual machines known to libvirt. A <em>transient</em> - guest only exists while it is running, and has no configuration file stored - on disk. A <em>persistent</em> guest maintains a configuration file on disk - even when it is not running. - </p> - - <p> - By default, a migration operation will not attempt to modify any configuration - files that may be stored on either the source or destination host. It is the - administrator, or management application's, responsibility to manage distribution - of configuration files (if desired). It is important to note that the <code>/etc/libvirt</code> - directory <strong>MUST NEVER BE SHARED BETWEEN HOSTS</strong>. There are some - typical scenarios that might be applicable: - </p> - - <ul> - <li>Centralized configuration files outside libvirt, in shared storage. A cluster - aware management application may maintain all the master guest configuration - files in a cluster filesystem. When attempting to start a guest, the config - will be read from the cluster FS and used to deploy a persistent guest. - For migration the configuration will need to be copied to the destination - host and removed on the original. - </li> - <li>Centralized configuration files outside libvirt, in a database. A data center - management application may not store configuration files at all. Instead it - may generate libvirt XML on the fly when a guest is booted. It will typically - use transient guests, and thus not have to consider configuration files during - migration. - </li> - <li>Distributed configuration inside libvirt. The configuration file for each - guest is copied to every host where the guest is able to run. Upon migration - the existing config merely needs to be updated with any changes. - </li> - <li>Ad-hoc configuration management inside libvirt. Each guest is tied to a - specific host and rarely migrated. When migration is required, the config - is moved from one host to the other. - </li> - </ul> - - <p> - As mentioned above, libvirt will not modify configuration files during - migration by default. The <code>virsh</code> command has two flags to - influence this behaviour. The <code>--undefinesource</code> flag - will cause the configuration file to be removed on the source host - after a successful migration. The <code>--persistent</code> flag will - cause a configuration file to be created on the destination host - after a successful migration. The following table summarizes the - configuration file handling in all possible state and flag - combinations. - </p> - - <table> - <thead> - <tr class="head"> - <th colspan="3">Before migration</th> - <th colspan="2">Flags</th> - <th colspan="3">After migration</th> - </tr> - <tr class="subhead"> - <th>Source type</th> - <th>Source config</th> - <th>Dest config</th> - <th>--undefinesource</th> - <th>--persistent</th> - <th>Dest type</th> - <th>Source config</th> - <th>Dest config</th> - </tr> - </thead> - <tbody> - <!-- src:N, dst:N --> - <tr> - <td>Transient</td> - <td class="n">N</td> - <td class="n">N</td> - <td class="n">N</td> - <td class="n">N</td> - <td>Transient</td> - <td class="n">N</td> - <td class="n">N</td> - </tr> - <tr> - <td>Transient</td> - <td class="n">N</td> - <td class="n">N</td> - <td class="y">Y</td> - <td class="n">N</td> - <td>Transient</td> - <td class="n">N</td> - <td class="n">N</td> - </tr> - <tr> - <td>Transient</td> - <td class="n">N</td> - <td class="n">N</td> - <td class="n">N</td> - <td class="y">Y</td> - <td>Persistent</td> - <td class="n">N</td> - <td class="y">Y</td> - </tr> - <tr> - <td>Transient</td> - <td class="n">N</td> - <td class="n">N</td> - <td class="y">Y</td> - <td class="y">Y</td> - <td>Persistent</td> - <td class="n">N</td> - <td class="y">Y</td> - </tr> - - <!-- src:N, dst:Y --> - <tr> - <td>Transient</td> - <td class="n">N</td> - <td class="y">Y</td> - <td class="n">N</td> - <td class="n">N</td> - <td>Persistent</td> - <td class="n">N</td> - <td class="y">Y<br/>(unchanged dest config)</td> - </tr> - <tr> - <td>Transient</td> - <td class="n">N</td> - <td class="y">Y</td> - <td class="y">Y</td> - <td class="n">N</td> - <td>Persistent</td> - <td class="n">N</td> - <td class="y">Y<br/>(unchanged dest config)</td> - </tr> - <tr> - <td>Transient</td> - <td class="n">N</td> - <td class="y">Y</td> - <td class="n">N</td> - <td class="y">Y</td> - <td>Persistent</td> - <td class="n">N</td> - <td class="y">Y<br/>(replaced with source)</td> - </tr> - <tr> - <td>Transient</td> - <td class="n">N</td> - <td class="y">Y</td> - <td class="y">Y</td> - <td class="y">Y</td> - <td>Persistent</td> - <td class="n">N</td> - <td class="y">Y<br/>(replaced with source)</td> - </tr> - - <!-- src:Y dst:N --> - <tr> - <td>Persistent</td> - <td class="y">Y</td> - <td class="n">N</td> - <td class="n">N</td> - <td class="n">N</td> - <td>Transient</td> - <td class="y">Y</td> - <td class="n">N</td> - </tr> - <tr> - <td>Persistent</td> - <td class="y">Y</td> - <td class="n">N</td> - <td class="y">Y</td> - <td class="n">N</td> - <td>Transient</td> - <td class="n">N</td> - <td class="n">N</td> - </tr> - <tr> - <td>Persistent</td> - <td class="y">Y</td> - <td class="n">N</td> - <td class="n">N</td> - <td class="y">Y</td> - <td>Persistent</td> - <td class="y">Y</td> - <td class="y">Y</td> - </tr> - <tr> - <td>Persistent</td> - <td class="y">Y</td> - <td class="n">N</td> - <td class="y">Y</td> - <td class="y">Y</td> - <td>Persistent</td> - <td class="n">N</td> - <td class="y">Y</td> - </tr> - - <!-- src:Y dst:Y --> - <tr> - <td>Persistent</td> - <td class="y">Y</td> - <td class="y">Y</td> - <td class="n">N</td> - <td class="n">N</td> - <td>Persistent</td> - <td class="y">Y</td> - <td class="y">Y<br/>(unchanged dest config)</td> - </tr> - <tr> - <td>Persistent</td> - <td class="y">Y</td> - <td class="y">Y</td> - <td class="y">Y</td> - <td class="n">N</td> - <td>Persistent</td> - <td class="n">N</td> - <td class="y">Y<br/>(unchanged dest config)</td> - </tr> - <tr> - <td>Persistent</td> - <td class="y">Y</td> - <td class="y">Y</td> - <td class="n">N</td> - <td class="y">Y</td> - <td>Persistent</td> - <td class="y">Y</td> - <td class="y">Y<br/>(replaced with source)</td> - </tr> - <tr> - <td>Persistent</td> - <td class="y">Y</td> - <td class="y">Y</td> - <td class="y">Y</td> - <td class="y">Y</td> - <td>Persistent</td> - <td class="n">N</td> - <td class="y">Y<br/>(replaced with source)</td> - </tr> - </tbody> - </table> - - <h2><a id="scenarios">Migration scenarios</a></h2> - - - <h3><a id="scenarionativedirect">Native migration, client to two libvirtd servers</a></h3> - - <p> - At an API level this requires use of virDomainMigrate, without the - VIR_MIGRATE_PEER2PEER flag set. The destination libvirtd server - will automatically determine the native hypervisor URI for migration - based off the primary hostname. To force migration over an alternate - network interface the optional hypervisor specific URI must be provided - </p> - - <pre> -syntax: virsh migrate GUESTNAME DEST-LIBVIRT-URI [HV-URI] - - -eg using default network interface - -virsh migrate web1 qemu+ssh://desthost/system -virsh migrate web1 xen+tls://desthost/system - - -eg using secondary network interface - -virsh migrate web1 qemu://desthost/system tcp://10.0.0.1/ - </pre> - - <p> - Supported by Xen, QEMU, VMware and VirtualBox drivers - </p> - - <h3><a id="scenarionativepeer2peer">Native migration, client to and peer2peer between, two libvirtd servers</a></h3> - - <p> - virDomainMigrate, with the VIR_MIGRATE_PEER2PEER flag set, - using the libvirt URI format for the 'uri' parameter. The - destination libvirtd server will automatically determine - the native hypervisor URI for migration, based off the - primary hostname. The optional uri parameter controls how - the source libvirtd connects to the destination libvirtd, - in case it is not accessible using the same address that - the client uses to connect to the destination, or a different - encryption/auth scheme is required. There is no - scope for forcing an alternative network interface for the - native migration data with this method. - </p> - - <p> - This mode cannot be invoked from virsh - </p> - - <p> - Supported by QEMU driver - </p> - - <h3><a id="scenariotunnelpeer2peer1">Tunnelled migration, client and peer2peer between two libvirtd servers</a></h3> - - <p> - virDomainMigrate, with the VIR_MIGRATE_PEER2PEER &amp; VIR_MIGRATE_TUNNELLED - flags set, using the libvirt URI format for the 'uri' parameter. The - destination libvirtd server will automatically determine - the native hypervisor URI for migration, based off the - primary hostname. The optional uri parameter controls how - the source libvirtd connects to the destination libvirtd, - in case it is not accessible using the same address that - the client uses to connect to the destination, or a different - encryption/auth scheme is required. The native hypervisor URI - format is not used at all. - </p> - - <p> - This mode cannot be invoked from virsh - </p> - - <p> - Supported by QEMU driver - </p> - - <h3><a id="nativedirectunmanaged">Native migration, client to one libvirtd server</a></h3> - - <p> - virDomainMigrateToURI, without the VIR_MIGRATE_PEER2PEER flag set, - using a hypervisor specific URI format for the 'uri' parameter. - There is no use or requirement for a destination libvirtd instance - at all. This is typically used when the hypervisor has its own - native management daemon available to handle incoming migration - attempts on the destination. - </p> - - <pre> -syntax: virsh migrate GUESTNAME HV-URI - - -eg using same libvirt URI for all connections - - </pre> - - <h3><a id="nativepeer2peer">Native migration, peer2peer between two libvirtd servers</a></h3> - - <p> - virDomainMigrateToURI, with the VIR_MIGRATE_PEER2PEER flag set, - using the libvirt URI format for the 'uri' parameter. The - destination libvirtd server will automatically determine - the native hypervisor URI for migration, based off the - primary hostname. There is no scope for forcing an alternative - network interface for the native migration data with this - method. The destination URI must be reachable using the source - libvirtd credentials (which are not necessarily the same as the - credentials of the client in connecting to the source). - </p> - - <pre> -syntax: virsh migrate GUESTNAME DEST-LIBVIRT-URI [ALT-DEST-LIBVIRT-URI] - - -eg using same libvirt URI for all connections - -virsh migrate --p2p web1 qemu+ssh://desthost/system - - -eg using different libvirt URI auth scheme for peer2peer connections - -virsh migrate --p2p web1 qemu+ssh://desthost/system qemu+tls:/desthost/system - - -eg using different libvirt URI hostname for peer2peer connections - -virsh migrate --p2p web1 qemu+ssh://desthost/system qemu+ssh://10.0.0.1/system - </pre> - - <p> - Supported by the QEMU driver - </p> - - <h3><a id="scenariotunnelpeer2peer2">Tunnelled migration, peer2peer between two libvirtd servers</a></h3> - - <p> - virDomainMigrateToURI, with the VIR_MIGRATE_PEER2PEER &amp; VIR_MIGRATE_TUNNELLED - flags set, using the libvirt URI format for the 'uri' parameter. The - destination libvirtd server will automatically determine - the native hypervisor URI for migration, based off the - primary hostname. The optional uri parameter controls how - the source libvirtd connects to the destination libvirtd, - in case it is not accessible using the same address that - the client uses to connect to the destination, or a different - encryption/auth scheme is required. The native hypervisor URI - format is not used at all. The destination URI must be - reachable using the source libvirtd credentials (which are not - necessarily the same as the credentials of the client in - connecting to the source). - </p> - - <pre> -syntax: virsh migrate GUESTNAME DEST-LIBVIRT-URI [ALT-DEST-LIBVIRT-URI] - - -eg using same libvirt URI for all connections - -virsh migrate --p2p --tunnelled web1 qemu+ssh://desthost/system - - -eg using different libvirt URI auth scheme for peer2peer connections - -virsh migrate --p2p --tunnelled web1 qemu+ssh://desthost/system qemu+tls:/desthost/system - - -eg using different libvirt URI hostname for peer2peer connections - -virsh migrate --p2p --tunnelled web1 qemu+ssh://desthost/system qemu+ssh://10.0.0.1/system - </pre> - - <p> - Supported by QEMU driver - </p> - - - <h3><a id="scenariounixsocket">Migration using only UNIX sockets</a></h3> - - <p> - In niche scenarios where libvirt daemon does not have access to the - network (e.g. running in a restricted container on a host that has - accessible network), when a management application wants to have complete - control over the transfer or when migrating between two containers on the - same host all the communication can be done using UNIX sockets. This - includes connecting to non-standard socket path for the destination - daemon, using UNIX sockets for hypervisor's communication or for the NBD - data transfer. All of that can be used with both peer2peer and direct - migration options. - </p> - - <p> - Example using <code>/tmp/migdir</code> as a directory representing the - same path visible from both libvirt daemons. That can be achieved by - bind-mounting the same directory to different containers running separate - daemons or forwarding connections to these sockets manually - (using <code>socat</code>, <code>netcat</code> or a custom piece of - software): - </p> - <pre> -virsh migrate --domain web1 [--p2p] --copy-storage-all - --desturi 'qemu+unix:///system?socket=/tmp/migdir/test-sock-driver' - --migrateuri 'unix:///tmp/migdir/test-sock-qemu' - --disks-uri unix:///tmp/migdir/test-sock-nbd - </pre> - - <p> - One caveat is that on SELinux-enabled systems all the sockets that the - hypervisor is going to connect to needs to have the proper context and - that is chosen before its creation by the process that creates it. That - is usually done by using <code>setsockcreatecon{,raw}()</code> functions. - Generally *system_r:system_u:svirt_socket_t:s0* should do the trick, but - check the SELinux rules and settings of your system. - </p> - - <p> - Supported by QEMU driver - </p> - - </body> -</html> diff --git a/docs/migration.rst b/docs/migration.rst new file mode 100644 index 0000000000..0a40600462 --- /dev/null +++ b/docs/migration.rst @@ -0,0 +1,458 @@ +=============== +Guest migration +=============== + +.. contents:: + +Migration of guests between hosts is a complicated problem with many possible +solutions, each with their own positive and negative points. For maximum +flexibility of both hypervisor integration, and administrator deployment, +libvirt implements several options for migration. + +Network data transports +----------------------- + +There are two options for the data transport used during migration, either the +hypervisor's own **native** transport, or **tunnelled** over a libvirtd +connection. + +Hypervisor native transport +~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +*Native* data transports may or may not support encryption, depending on the +hypervisor in question, but will typically have the lowest computational costs +by minimising the number of data copies involved. The native data transports +will also require extra hypervisor-specific network configuration steps by the +administrator when deploying a host. For some hypervisors, it might be necessary +to open up a large range of ports on the firewall to allow multiple concurrent +migration operations. + +Modern hypervisors support TLS for encryption and authentication of the +migration connections which can be enabled using the ``VIR_MIGRATE_TLS`` flag. +The *qemu* hypervisor driver allows users to force use of TLS via the +``migrate_tls_force`` knob configured in ``/etc/libvirt/qemu.conf``. + +|Migration native path| + +libvirt tunnelled transport +~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +*Tunnelled* data transports will always be capable of strong encryption since +they are able to leverage the capabilities built in to the libvirt RPC protocol. +The downside of a tunnelled transport, however, is that there will be extra data +copies involved on both the source and destinations hosts as the data is moved +between libvirtd and the hypervisor. This is likely to be a more significant +problem for guests with very large RAM sizes, which dirty memory pages quickly. +On the deployment side, tunnelled transports do not require any extra network +configuration over and above what's already required for general libvirtd +`remote access <remote.html>`__, and there is only need for a single port to be +open on the firewall to support multiple concurrent migration operations. + +*Note:* Certain features such as migration of non-shared storage +(``VIR_MIGRATE_NON_SHARED_DISK``), the multi-connection migration +(``VIR_MIGRATE_PARALLEL``), or post-copy migration (``VIR_MIGRATE_POSTCOPY``) +may not be available when using libvirt's tunnelling. + +|Migration tunnel path| + +Communication control paths/flows +--------------------------------- + +Migration of virtual machines requires close co-ordination of the two hosts +involved, as well as the application invoking the migration, which may be on the +source, the destination, or a third host. + +Managed direct migration +~~~~~~~~~~~~~~~~~~~~~~~~ + +With *managed direct* migration, the libvirt client process controls the various +phases of migration. The client application must be able to connect and +authenticate with the libvirtd daemons on both the source and destination hosts. +There is no need for the two libvirtd daemons to communicate with each other. If +the client application crashes, or otherwise loses its connection to libvirtd +during the migration process, an attempt will be made to abort the migration and +restart the guest CPUs on the source host. There may be scenarios where this +cannot be safely done, in which cases the guest will be left paused on one or +both of the hosts. + +|Migration direct, managed| + +Managed peer to peer migration +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +With *peer to peer* migration, the libvirt client process only talks to the +libvirtd daemon on the source host. The source libvirtd daemon controls the +entire migration process itself, by directly connecting the destination host +libvirtd. If the client application crashes, or otherwise loses its connection +to libvirtd, the migration process will continue uninterrupted until completion. +Note that the source libvirtd uses its own credentials (typically root) to +connect to the destination, rather than the credentials used by the client to +connect to the source; if these differ, it is common to run into a situation +where a client can connect to the destination directly but the source cannot +make the connection to set up the peer-to-peer migration. + +|Migration peer-to-peer| + +Unmanaged direct migration +~~~~~~~~~~~~~~~~~~~~~~~~~~ + +With *unmanaged direct* migration, neither the libvirt client or libvirtd daemon +control the migration process. Control is instead delegated to the hypervisor's +over management services (if any). The libvirt client merely initiates the +migration via the hypervisor's management layer. If the libvirt client or +libvirtd crash, the migration process will continue uninterrupted until +completion. + +|Migration direct, unmanaged| + +Data security +------------- + +Since the migration data stream includes a complete copy of the guest OS RAM, +snooping of the migration data stream may allow compromise of sensitive guest +information. If the virtualization hosts have multiple network interfaces, or if +the network switches support tagged VLANs, then it is very desirable to separate +guest network traffic from migration or management traffic. + +In some scenarios, even a separate network for migration data may not offer +sufficient security. In this case it is possible to apply encryption to the +migration data stream. If the hypervisor does not itself offer encryption, then +the libvirt tunnelled migration facility should be used. + +Offline migration +----------------- + +Offline migration transfers the inactive definition of a domain (which may or +may not be active). After successful completion, the domain remains in its +current state on the source host and is defined but inactive on the destination +host. It's a bit more clever than ``virsh dumpxml`` on source host followed by +``virsh define`` on destination host, as offline migration will run the +pre-migration hook to update the domain XML on destination host. Currently, +copying non-shared storage or other file based storages (e.g. UEFI variable +storage) is not supported during offline migration. + +Migration URIs +-------------- + +Initiating a guest migration requires the client application to specify up to +three URIs, depending on the choice of control flow and/or APIs used. The first +URI is that of the libvirt connection to the source host, where the virtual +guest is currently running. The second URI is that of the libvirt connection to +the destination host, where the virtual guest will be moved to (and in +peer-to-peer migrations, this is from the perspective of the source, not the +client). The third URI is a hypervisor specific URI used to control how the +guest will be migrated. With any managed migration flow, the first and second +URIs are compulsory, while the third URI is optional. With the unmanaged direct +migration mode, the first and third URIs are compulsory and the second URI is +not used. + +Ordinarily management applications only need to care about the first and second +URIs, which are both in the normal libvirt connection URI format. Libvirt will +then automatically determine the hypervisor specific URI, by looking up the +target host's configured hostname. There are a few scenarios where the +management application may wish to have direct control over the third URI. + +#. The configured hostname is incorrect, or DNS is broken. If a host has a + hostname which will not resolve to match one of its public IP addresses, then + libvirt will generate an incorrect URI. In this case the management + application should specify the hypervisor specific URI explicitly, using an + IP address, or a correct hostname. +#. The host has multiple network interfaces. If a host has multiple network + interfaces, it might be desirable for the migration data stream to be sent + over a specific interface for either security or performance reasons. In this + case the management application should specify the hypervisor specific URI, + using an IP address associated with the network to be used. +#. The firewall restricts what ports are available. When libvirt generates a + migration URI it will pick a port number using hypervisor specific rules. + Some hypervisors only require a single port to be open in the firewalls, + while others require a whole range of port numbers. In the latter case the + management application may wish to choose a specific port number outside the + default range in order to comply with local firewall policies. +#. The second URI uses UNIX transport method. In this advanced case libvirt + should not guess a \*migrateuri\* and it should be specified using UNIX + socket path URI: ``unix:///path/to/socket``. + +Configuration file handling +--------------------------- + +There are two types of virtual machines known to libvirt. A *transient* guest +only exists while it is running, and has no configuration file stored on disk. A +*persistent* guest maintains a configuration file on disk even when it is not +running. + +By default, a migration operation will not attempt to modify any configuration +files that may be stored on either the source or destination host. It is the +administrator, or management application's, responsibility to manage +distribution of configuration files (if desired). It is important to note that +the ``/etc/libvirt`` directory **MUST NEVER BE SHARED BETWEEN HOSTS**. There are +some typical scenarios that might be applicable: + +- Centralized configuration files outside libvirt, in shared storage. A cluster + aware management application may maintain all the master guest configuration + files in a cluster filesystem. When attempting to start a guest, the config + will be read from the cluster FS and used to deploy a persistent guest. For + migration the configuration will need to be copied to the destination host + and removed on the original. +- Centralized configuration files outside libvirt, in a database. A data center + management application may not store configuration files at all. Instead it + may generate libvirt XML on the fly when a guest is booted. It will typically + use transient guests, and thus not have to consider configuration files + during migration. +- Distributed configuration inside libvirt. The configuration file for each + guest is copied to every host where the guest is able to run. Upon migration + the existing config merely needs to be updated with any changes. +- Ad-hoc configuration management inside libvirt. Each guest is tied to a + specific host and rarely migrated. When migration is required, the config is + moved from one host to the other. + +As mentioned above, libvirt will not modify configuration files during migration +by default. The ``virsh`` command has two flags to influence this behaviour. The +``--undefinesource`` flag will cause the configuration file to be removed on the +source host after a successful migration. The ``--persistent`` flag will cause a +configuration file to be created on the destination host after a successful +migration. The following table summarizes the configuration file handling in all +possible state and flag combinations. + ++-------------------+-------------------+-------------------+-------------------+-------------------+-------------------+-------------------+-------------------+ +| Before migration | Flags | After migration | ++-------------------+-------------------+-------------------+-------------------+-------------------+-------------------+-------------------+-------------------+ +| Source type | Source config | Dest config | --undefinesource | --persistent | Dest type | Source config | Dest config | ++===================+===================+===================+===================+===================+===================+===================+===================+ +| Transient | N | N | N | N | Transient | N | N | ++-------------------+-------------------+-------------------+-------------------+-------------------+-------------------+-------------------+-------------------+ +| Transient | N | N | Y | N | Transient | N | N | ++-------------------+-------------------+-------------------+-------------------+-------------------+-------------------+-------------------+-------------------+ +| Transient | N | N | N | Y | Persistent | N | Y | ++-------------------+-------------------+-------------------+-------------------+-------------------+-------------------+-------------------+-------------------+ +| Transient | N | N | Y | Y | Persistent | N | Y | ++-------------------+-------------------+-------------------+-------------------+-------------------+-------------------+-------------------+-------------------+ +| Transient | N | Y | N | N | Persistent | N | Y | +| | | | | | | | (unchanged dest | +| | | | | | | | config) | ++-------------------+-------------------+-------------------+-------------------+-------------------+-------------------+-------------------+-------------------+ +| Transient | N | Y | Y | N | Persistent | N | Y | +| | | | | | | | (unchanged dest | +| | | | | | | | config) | ++-------------------+-------------------+-------------------+-------------------+-------------------+-------------------+-------------------+-------------------+ +| Transient | N | Y | N | Y | Persistent | N | Y | +| | | | | | | | (replaced with | +| | | | | | | | source) | ++-------------------+-------------------+-------------------+-------------------+-------------------+-------------------+-------------------+-------------------+ +| Transient | N | Y | Y | Y | Persistent | N | Y | +| | | | | | | | (replaced with | +| | | | | | | | source) | ++-------------------+-------------------+-------------------+-------------------+-------------------+-------------------+-------------------+-------------------+ +| Persistent | Y | N | N | N | Transient | Y | N | ++-------------------+-------------------+-------------------+-------------------+-------------------+-------------------+-------------------+-------------------+ +| Persistent | Y | N | Y | N | Transient | N | N | ++-------------------+-------------------+-------------------+-------------------+-------------------+-------------------+-------------------+-------------------+ +| Persistent | Y | N | N | Y | Persistent | Y | Y | ++-------------------+-------------------+-------------------+-------------------+-------------------+-------------------+-------------------+-------------------+ +| Persistent | Y | N | Y | Y | Persistent | N | Y | ++-------------------+-------------------+-------------------+-------------------+-------------------+-------------------+-------------------+-------------------+ +| Persistent | Y | Y | N | N | Persistent | Y | Y | +| | | | | | | | (unchanged dest | +| | | | | | | | config) | ++-------------------+-------------------+-------------------+-------------------+-------------------+-------------------+-------------------+-------------------+ +| Persistent | Y | Y | Y | N | Persistent | N | Y | +| | | | | | | | (unchanged dest | +| | | | | | | | config) | ++-------------------+-------------------+-------------------+-------------------+-------------------+-------------------+-------------------+-------------------+ +| Persistent | Y | Y | N | Y | Persistent | Y | Y | +| | | | | | | | (replaced with | +| | | | | | | | source) | ++-------------------+-------------------+-------------------+-------------------+-------------------+-------------------+-------------------+-------------------+ +| Persistent | Y | Y | Y | Y | Persistent | N | Y | +| | | | | | | | (replaced with | +| | | | | | | | source) | ++-------------------+-------------------+-------------------+-------------------+-------------------+-------------------+-------------------+-------------------+ + +Migration scenarios +------------------- + +Native migration, client to two libvirtd servers +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +At an API level this requires use of virDomainMigrate, without the +VIR_MIGRATE_PEER2PEER flag set. The destination libvirtd server will +automatically determine the native hypervisor URI for migration based off the +primary hostname. To force migration over an alternate network interface the +optional hypervisor specific URI must be provided + +:: + + syntax: virsh migrate GUESTNAME DEST-LIBVIRT-URI [HV-URI] + + + eg using default network interface + + virsh migrate web1 qemu+ssh://desthost/system + virsh migrate web1 xen+tls://desthost/system + + + eg using secondary network interface + + virsh migrate web1 qemu://desthost/system tcp://10.0.0.1/ + +Supported by Xen, QEMU, VMware and VirtualBox drivers + +Native migration, client to and peer2peer between, two libvirtd servers +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +virDomainMigrate, with the VIR_MIGRATE_PEER2PEER flag set, using the libvirt URI +format for the 'uri' parameter. The destination libvirtd server will +automatically determine the native hypervisor URI for migration, based off the +primary hostname. The optional uri parameter controls how the source libvirtd +connects to the destination libvirtd, in case it is not accessible using the +same address that the client uses to connect to the destination, or a different +encryption/auth scheme is required. There is no scope for forcing an alternative +network interface for the native migration data with this method. + +This mode cannot be invoked from virsh + +Supported by QEMU driver + +Tunnelled migration, client and peer2peer between two libvirtd servers +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +virDomainMigrate, with the VIR_MIGRATE_PEER2PEER & VIR_MIGRATE_TUNNELLED flags +set, using the libvirt URI format for the 'uri' parameter. The destination +libvirtd server will automatically determine the native hypervisor URI for +migration, based off the primary hostname. The optional uri parameter controls +how the source libvirtd connects to the destination libvirtd, in case it is not +accessible using the same address that the client uses to connect to the +destination, or a different encryption/auth scheme is required. The native +hypervisor URI format is not used at all. + +This mode cannot be invoked from virsh + +Supported by QEMU driver + +Native migration, client to one libvirtd server +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +virDomainMigrateToURI, without the VIR_MIGRATE_PEER2PEER flag set, using a +hypervisor specific URI format for the 'uri' parameter. There is no use or +requirement for a destination libvirtd instance at all. This is typically used +when the hypervisor has its own native management daemon available to handle +incoming migration attempts on the destination. + +:: + + syntax: virsh migrate GUESTNAME HV-URI + + + eg using same libvirt URI for all connections + + +Native migration, peer2peer between two libvirtd servers +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +virDomainMigrateToURI, with the VIR_MIGRATE_PEER2PEER flag set, using the +libvirt URI format for the 'uri' parameter. The destination libvirtd server will +automatically determine the native hypervisor URI for migration, based off the +primary hostname. There is no scope for forcing an alternative network interface +for the native migration data with this method. The destination URI must be +reachable using the source libvirtd credentials (which are not necessarily the +same as the credentials of the client in connecting to the source). + +:: + + syntax: virsh migrate GUESTNAME DEST-LIBVIRT-URI [ALT-DEST-LIBVIRT-URI] + + + eg using same libvirt URI for all connections + + virsh migrate --p2p web1 qemu+ssh://desthost/system + + + eg using different libvirt URI auth scheme for peer2peer connections + + virsh migrate --p2p web1 qemu+ssh://desthost/system qemu+tls:/desthost/system + + + eg using different libvirt URI hostname for peer2peer connections + + virsh migrate --p2p web1 qemu+ssh://desthost/system qemu+ssh://10.0.0.1/system + +Supported by the QEMU driver + +Tunnelled migration, peer2peer between two libvirtd servers +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +virDomainMigrateToURI, with the VIR_MIGRATE_PEER2PEER & VIR_MIGRATE_TUNNELLED +flags set, using the libvirt URI format for the 'uri' parameter. The destination +libvirtd server will automatically determine the native hypervisor URI for +migration, based off the primary hostname. The optional uri parameter controls +how the source libvirtd connects to the destination libvirtd, in case it is not +accessible using the same address that the client uses to connect to the +destination, or a different encryption/auth scheme is required. The native +hypervisor URI format is not used at all. The destination URI must be reachable +using the source libvirtd credentials (which are not necessarily the same as the +credentials of the client in connecting to the source). + +:: + + syntax: virsh migrate GUESTNAME DEST-LIBVIRT-URI [ALT-DEST-LIBVIRT-URI] + + + eg using same libvirt URI for all connections + + virsh migrate --p2p --tunnelled web1 qemu+ssh://desthost/system + + + eg using different libvirt URI auth scheme for peer2peer connections + + virsh migrate --p2p --tunnelled web1 qemu+ssh://desthost/system qemu+tls:/desthost/system + + + eg using different libvirt URI hostname for peer2peer connections + + virsh migrate --p2p --tunnelled web1 qemu+ssh://desthost/system qemu+ssh://10.0.0.1/system + +Supported by QEMU driver + +Migration using only UNIX sockets +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +In niche scenarios where libvirt daemon does not have access to the network +(e.g. running in a restricted container on a host that has accessible network), +when a management application wants to have complete control over the transfer +or when migrating between two containers on the same host all the communication +can be done using UNIX sockets. This includes connecting to non-standard socket +path for the destination daemon, using UNIX sockets for hypervisor's +communication or for the NBD data transfer. All of that can be used with both +peer2peer and direct migration options. + +Example using ``/tmp/migdir`` as a directory representing the same path visible +from both libvirt daemons. That can be achieved by bind-mounting the same +directory to different containers running separate daemons or forwarding +connections to these sockets manually (using ``socat``, ``netcat`` or a custom +piece of software): + +:: + + virsh migrate --domain web1 [--p2p] --copy-storage-all + --desturi 'qemu+unix:///system?socket=/tmp/migdir/test-sock-driver' + --migrateuri 'unix:///tmp/migdir/test-sock-qemu' + --disks-uri unix:///tmp/migdir/test-sock-nbd + +One caveat is that on SELinux-enabled systems all the sockets that the +hypervisor is going to connect to needs to have the proper context and that is +chosen before its creation by the process that creates it. That is usually done +by using ``setsockcreatecon{,raw}()`` functions. Generally +\*system_r:system_u:svirt_socket_t:s0\* should do the trick, but check the +SELinux rules and settings of your system. + +Supported by QEMU driver + +.. |Migration native path| image:: migration-native.png + :class: diagram +.. |Migration tunnel path| image:: migration-tunnel.png + :class: diagram +.. |Migration direct, managed| image:: migration-managed-direct.png + :class: diagram +.. |Migration peer-to-peer| image:: migration-managed-p2p.png + :class: diagram +.. |Migration direct, unmanaged| image:: migration-unmanaged-direct.png + :class: diagram -- 2.31.1

Signed-off-by: Peter Krempa <pkrempa(a)redhat.com&gt; --- NEWS.rst | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/NEWS.rst b/NEWS.rst index 4d690ff64b..a4252d555d 100644 --- a/NEWS.rst +++ b/NEWS.rst @@ -17,6 +17,18 @@ v8.0.0 (unreleased) * **New features** + * qemu: Synchronous write mode for disk copy operations + + The ``blockdev-mirror`` block job supports a mode where writes from the VM + are synchronously propagated to the destination of the copy. This ensures + that the job will converge under heavy I/O. + + Implement the mode for the copy blockjob as + ``VIR_DOMAIN_BLOCK_COPY_SYNCHRONOUS_WRITES`` flag exposed via + ``virsh blockcopy --synchronous-writes`` and for non-shared storage migration + as ``VIR_MIGRATE_NON_SHARED_SYNCHRONOUS_WRITES`` exposed via + ``virsh migrate --copy-storage-synchronous-writes``. + * **Improvements** * **Bug fixes** -- 2.31.1