From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 3A99AC02183 for ; Fri, 17 Jan 2025 14:43:39 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1tYnYW-0001Am-E2; Fri, 17 Jan 2025 09:42:40 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1tYnYS-00019N-Ui for qemu-devel@nongnu.org; Fri, 17 Jan 2025 09:42:37 -0500 Received: from smtp-out2.suse.de ([195.135.223.131]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1tYnYQ-0004Kd-5A for qemu-devel@nongnu.org; Fri, 17 Jan 2025 09:42:36 -0500 Received: from imap1.dmz-prg2.suse.org (unknown [10.150.64.97]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id 826701F454; Fri, 17 Jan 2025 14:42:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1737124952; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=mA77vTevdOvKsoXFtLVxUJene3XFmNMIqIEDO397wNo=; b=pR51k8OFxBh8iwg+S9ZTbKdNWn0UwZSufas9UQLbwExlB4Lt3nYPPuTEnZxvsOo8wAIsCO bPoFR1rWKZSSvvd7HFiJMeC0JF9lmJouN5ChmN1NpOXBGBlFRenOjMA/bwZGrxXn6CSiv/ fHhRyB4N94l7KDlS1hh3o8B5nUdShU0= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1737124952; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=mA77vTevdOvKsoXFtLVxUJene3XFmNMIqIEDO397wNo=; b=yPQUNxY/aXNV5+JBfNpJLEtzGdl1fagHWpoWGnBZ6AegIdGKDdgAF5+WeMyfr6wRRaNvyX /Yxifk3uOc1pSTBQ== Authentication-Results: smtp-out2.suse.de; none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1737124952; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=mA77vTevdOvKsoXFtLVxUJene3XFmNMIqIEDO397wNo=; b=pR51k8OFxBh8iwg+S9ZTbKdNWn0UwZSufas9UQLbwExlB4Lt3nYPPuTEnZxvsOo8wAIsCO bPoFR1rWKZSSvvd7HFiJMeC0JF9lmJouN5ChmN1NpOXBGBlFRenOjMA/bwZGrxXn6CSiv/ fHhRyB4N94l7KDlS1hh3o8B5nUdShU0= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1737124952; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=mA77vTevdOvKsoXFtLVxUJene3XFmNMIqIEDO397wNo=; b=yPQUNxY/aXNV5+JBfNpJLEtzGdl1fagHWpoWGnBZ6AegIdGKDdgAF5+WeMyfr6wRRaNvyX /Yxifk3uOc1pSTBQ== Received: from imap1.dmz-prg2.suse.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by imap1.dmz-prg2.suse.org (Postfix) with ESMTPS id D9B4F13332; Fri, 17 Jan 2025 14:42:31 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id PFmxJVdsimduaQAAD6G6ig (envelope-from ); Fri, 17 Jan 2025 14:42:31 +0000 From: Fabiano Rosas To: Steve Sistare , qemu-devel@nongnu.org Cc: Peter Xu , David Hildenbrand , Marcel Apfelbaum , Eduardo Habkost , Philippe Mathieu-Daude , Paolo Bonzini , "Daniel P. Berrange" , Markus Armbruster , Steve Sistare Subject: Re: [PATCH V7 24/24] migration: cpr-transfer documentation In-Reply-To: <1736967650-129648-25-git-send-email-steven.sistare@oracle.com> References: <1736967650-129648-1-git-send-email-steven.sistare@oracle.com> <1736967650-129648-25-git-send-email-steven.sistare@oracle.com> Date: Fri, 17 Jan 2025 11:42:29 -0300 Message-ID: <87tt9xec2y.fsf@suse.de> MIME-Version: 1.0 Content-Type: text/plain X-Spamd-Result: default: False [-2.80 / 50.00]; BAYES_HAM(-3.00)[100.00%]; SUSPICIOUS_RECIPS(1.50)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; FREEMAIL_ENVRCPT(0.00)[gmail.com]; TAGGED_RCPT(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; ARC_NA(0.00)[]; MISSING_XM_UA(0.00)[]; RCVD_TLS_ALL(0.00)[]; MIME_TRACE(0.00)[0:+]; RCPT_COUNT_SEVEN(0.00)[11]; MID_RHS_MATCH_FROM(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FROM_HAS_DN(0.00)[]; FREEMAIL_CC(0.00)[redhat.com,gmail.com,habkost.net,linaro.org,oracle.com]; TO_DN_SOME(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; TO_MATCH_ENVRCPT_ALL(0.00)[]; FUZZY_BLOCKED(0.00)[rspamd.com]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:mid] Received-SPF: pass client-ip=195.135.223.131; envelope-from=farosas@suse.de; helo=smtp-out2.suse.de X-Spam_score_int: -43 X-Spam_score: -4.4 X-Spam_bar: ---- X-Spam_report: (-4.4 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_MED=-2.3, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Steve Sistare writes: > Add documentation for the cpr-transfer migration mode. > > Signed-off-by: Steve Sistare > Reviewed-by: Peter Xu > --- > docs/devel/migration/CPR.rst | 182 ++++++++++++++++++++++++++++++++++++++++++- > 1 file changed, 180 insertions(+), 2 deletions(-) > > diff --git a/docs/devel/migration/CPR.rst b/docs/devel/migration/CPR.rst > index 63c3647..d6021d5 100644 > --- a/docs/devel/migration/CPR.rst > +++ b/docs/devel/migration/CPR.rst > @@ -5,7 +5,7 @@ CPR is the umbrella name for a set of migration modes in which the > VM is migrated to a new QEMU instance on the same host. It is > intended for use when the goal is to update host software components > that run the VM, such as QEMU or even the host kernel. At this time, > -cpr-reboot is the only available mode. > +the cpr-reboot and cpr-transfer modes are available. > > Because QEMU is restarted on the same host, with access to the same > local devices, CPR is allowed in certain cases where normal migration > @@ -53,7 +53,7 @@ RAM is copied to the migration URI. > Outgoing: > * Set the migration mode parameter to ``cpr-reboot``. > * Set the ``x-ignore-shared`` capability if desired. > - * Issue the ``migrate`` command. It is recommended the the URI be a > + * Issue the ``migrate`` command. It is recommended the URI be a > ``file`` type, but one can use other types such as ``exec``, > provided the command captures all the data from the outgoing side, > and provides all the data to the incoming side. > @@ -145,3 +145,181 @@ Caveats > > cpr-reboot mode may not be used with postcopy, background-snapshot, > or COLO. > + > +cpr-transfer mode > +----------------- > + > +This mode allows the user to transfer a guest to a new QEMU instance > +on the same host with minimal guest pause time, by preserving guest > +RAM in place, albeit with new virtual addresses in new QEMU. Devices > +and their pinned memory pages will also be preserved in a future QEMU > +release. > + > +The user starts new QEMU on the same host as old QEMU, with command- > +line arguments to create the same machine, plus the ``-incoming`` > +option for the main migration channel, like normal live migration. > +In addition, the user adds a second -incoming option with channel > +type ``cpr``. This CPR channel must support file descriptor transfer > +with SCM_RIGHTS, i.e. it must be a UNIX domain socket. > + > +To initiate CPR, the user issues a migrate command to old QEMU, > +adding a second migration channel of type ``cpr`` in the channels > +argument. Old QEMU stops the VM, saves state to the migration > +channels, and enters the postmigrate state. Execution resumes in > +new QEMU. > + > +New QEMU reads the CPR channel before opening a monitor, hence > +the CPR channel cannot be specified in the list of channels for a > +migrate-incoming command. It may only be specified on the command > +line. > + > +Usage > +^^^^^ > + > +Memory backend objects must have the ``share=on`` attribute. > + > +The VM must be started with the ``-machine aux-ram-share=on`` > +option. This causes implicit RAM blocks (those not described by > +a memory-backend object) to be allocated by mmap'ing a memfd. > +Examples include VGA and ROM. > + > +Outgoing: > + * Set the migration mode parameter to ``cpr-transfer``. > + * Issue the ``migrate`` command, containing a main channel and > + a cpr channel. > + > +Incoming: > + * Start new QEMU with two ``-incoming`` options. > + * If the VM was running when the outgoing ``migrate`` command was > + issued, then QEMU automatically resumes VM execution. > + > +Caveats > +^^^^^^^ > + > +cpr-transfer mode may not be used with postcopy, background-snapshot, > +or COLO. > + > +memory-backend-epc is not supported. > + > +The main incoming migration channel address cannot be a file type. > + > +If the main incoming channel address is an inet socket, then the port > +cannot be 0 (meaning dynamically choose a port). > + > +When using ``-incoming defer``, you must issue the migrate command to > +old QEMU before issuing any monitor commands to new QEMU, because new > +QEMU blocks waiting to read from the cpr channel before starting its > +monitor, and old QEMU does not write to the channel until the migrate > +command is issued. However, new QEMU does not open and read the > +main migration channel until you issue the migrate incoming command. > + > +Example 1: incoming channel > +^^^^^^^^^^^^^^^^^^^^^^^^^^^ > + > +In these examples, we simply restart the same version of QEMU, but > +in a real scenario one would start new QEMU on the incoming side. > +Note that new QEMU does not print the monitor prompt until old QEMU > +has issued the migrate command. The outgoing side uses QMP because > +HMP cannot specify a CPR channel. Some QMP responses are omitted for > +brevity. > + > +:: > + > + Outgoing: Incoming: > + > + # qemu-kvm -qmp stdio > + -object memory-backend-file,id=ram0,size=4G, > + mem-path=/dev/shm/ram0,share=on -m 4G > + -machine aux-ram-share=on > + ... > + # qemu-kvm -monitor stdio > + -incoming tcp:0:44444 > + -incoming '{"channel-type": "cpr", > + "addr": { "transport": "socket", > + "type": "unix", "path": "cpr.sock"}}' > + ... I'm attempting this and not having much success. Surely I'm missing something: $ qemu-system-x86_64 -cpu host -smp 16 -machine pc,accel=kvm \ -drive id=drive0,if=none,format=qcow2,file=img.qcow2 \ -device virtio-blk-pci,id=image1,drive=drive0,bootindex=0 \ -qmp unix:./dst-qmp.sock,server,wait=off \ -nographic -serial mon:stdio \ -object memory-backend-file,id=ram0,size=4G,mem-path=/dev/shm/ram0,share=on \ -m 4G -machine aux-ram-share=on \ -incoming tcp:0:44444 \ -incoming '{"channel-type": "cpr", "addr": { "transport": "socket", "type": "unix", "path": "cpr.sock"}}' \ -trace loadvm_* -trace cpr_* -trace migration_* -trace migrate_* -trace qemu_loadvm_* cpr_transfer_input cpr.sock cpr_state_load cpr-transfer mode cpr_find_fd pc.bios, id 0 returns 15 cpr_find_fd pc.rom, id 0 returns 14 cpr_find_fd 0000:00:02.0/vga.vram, id 0 returns 13 cpr_find_fd 0000:00:02.0/vga.rom, id 0 returns 12 cpr_find_fd 0000:00:03.0/e1000.rom, id 0 returns 11 cpr_find_fd /rom@etc/acpi/tables, id 0 returns 10 cpr_find_fd /rom@etc/table-loader, id 0 returns 8 cpr_find_fd /rom@etc/acpi/rsdp, id 0 returns 3 migrate_set_state new state setup migration_socket_incoming_accepted migration_set_incoming_channel ioc=0x564dc31e7000 ioctype=qio-channel-socket migrate_set_state new state active loadvm_state_setup qemu_loadvm_state_section 1 qemu_loadvm_state_section_startfull 2(ram) 0 4 qemu_loadvm_state_section 3 qemu_loadvm_state_section_partend 2 qemu_loadvm_state_section 4 qemu_loadvm_state_section_startfull 0(timer) 0 2 qemu_loadvm_state_section 4 qemu_loadvm_state_section_startfull 1(slirp) 0 4 qemu_loadvm_state_section 4 qemu_loadvm_state_section_startfull 4(cpu_common) 0 1 qemu_loadvm_state_section 4 qemu_loadvm_state_section_startfull 5(cpu) 0 12 qemu_loadvm_state_section 4 qemu_loadvm_state_section_startfull 6(kvm-tpr-opt) 0 1 qemu-system-x86_64: error while loading state for instance 0x0 of device 'kvm-tpr-opt' qemu_loadvm_state_post_main -1 migrate_set_state new state failed migrate_error error=load of migration failed: Operation not permitted loadvm_state_cleanup qemu-system-x86_64: load of migration failed: Operation not permitted > + {"execute":"qmp_capabilities"} > + > + {"execute": "query-status"} > + {"return": {"status": "running", > + "running": true}} > + > + {"execute":"migrate-set-parameters", > + "arguments":{"mode":"cpr-transfer"}} > + > + {"execute": "migrate", "arguments": { "channels": [ > + {"channel-type": "main", > + "addr": { "transport": "socket", "type": "inet", > + "host": "0", "port": "44444" }}, > + {"channel-type": "cpr", > + "addr": { "transport": "socket", "type": "unix", > + "path": "cpr.sock" }}]}} > + > + QEMU 10.0.50 monitor > + (qemu) info status > + VM status: running > + > + {"execute": "query-status"} > + {"return": {"status": "postmigrate", > + "running": false}} > + > +Example 2: incoming defer > +^^^^^^^^^^^^^^^^^^^^^^^^^ > + > +This example uses ``-incoming defer`` to hot plug a device before > +accepting the main migration channel. Again note you must issue the > +migrate command to old QEMU before you can issue any monitor > +commands to new QEMU. > + > + > +:: > + > + Outgoing: Incoming: > + > + # qemu-kvm -monitor stdio > + -object memory-backend-file,id=ram0,size=4G, > + mem-path=/dev/shm/ram0,share=on -m 4G > + -machine aux-ram-share=on > + ... > + # qemu-kvm -monitor stdio > + -incoming defer > + -incoming '{"channel-type": "cpr", > + "addr": { "transport": "socket", > + "type": "unix", "path": "cpr.sock"}}' > + ... > + {"execute":"qmp_capabilities"} > + > + {"execute": "device_add", > + "arguments": {"driver": "pcie-root-port"}} > + > + {"execute":"migrate-set-parameters", > + "arguments":{"mode":"cpr-transfer"}} > + > + {"execute": "migrate", "arguments": { "channels": [ > + {"channel-type": "main", > + "addr": { "transport": "socket", "type": "inet", > + "host": "0", "port": "44444" }}, > + {"channel-type": "cpr", > + "addr": { "transport": "socket", "type": "unix", > + "path": "cpr.sock" }}]}} > + > + QEMU 10.0.50 monitor > + (qemu) info status > + VM status: paused (inmigrate) > + (qemu) device_add pcie-root-port > + (qemu) migrate_incoming tcp:0:44444 > + (qemu) info status > + VM status: running > + > + {"execute": "query-status"} > + {"return": {"status": "postmigrate", > + "running": false}} > + > +Futures > +^^^^^^^ > + > +cpr-transfer mode is based on a capability to transfer open file > +descriptors from old to new QEMU. In the future, descriptors for > +vfio, iommufd, vhost, and char devices could be transferred, > +preserving those devices and their kernel state without interruption, > +even if they do not explicitly support live migration.