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 lists1p.gnu.org (lists1p.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 6D2EECD6E57 for ; Tue, 2 Jun 2026 13:38:32 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists1p.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1wUPJb-0008CI-MR; Tue, 02 Jun 2026 09:37:55 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists1p.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1wUPJZ-0008Aj-BB for qemu-devel@nongnu.org; Tue, 02 Jun 2026 09:37:53 -0400 Received: from smtp-out1.suse.de ([195.135.223.130]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1wUPJW-0008I7-6p for qemu-devel@nongnu.org; Tue, 02 Jun 2026 09:37:53 -0400 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-out1.suse.de (Postfix) with ESMTPS id 612FF6B0ED; Tue, 2 Jun 2026 13:37:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1780407467; 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=rPDZWrQrvp8j1kbdE+WXc6uZg5H54UA0eadxPXQn/+0=; b=A2yX1BSKNT9CI3rGdbwEfpxSaJbO8pef939Qdgcj03vmv9OAGXwpEy9gE8sLCdwmh4aW+K c6MV9xKu9mIYGi+CHbTtD7LeB9vIf1sXWOBQWwrd6Zi3PzEo5lgtnVg3DEKSwlpnSaG3g9 hIUmhyAJTquOWf4p11Q5jkwSFHB8jrI= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1780407467; 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=rPDZWrQrvp8j1kbdE+WXc6uZg5H54UA0eadxPXQn/+0=; b=y9CVPRB4UvydLH4kCwn/pFk4zeYqYR/GoYjnrVQ1zYkwmiQhgnMpY/EGzZ/L4/do38MfQ9 oteKt1T60uBDCECw== Authentication-Results: smtp-out1.suse.de; none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1780407467; 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=rPDZWrQrvp8j1kbdE+WXc6uZg5H54UA0eadxPXQn/+0=; b=A2yX1BSKNT9CI3rGdbwEfpxSaJbO8pef939Qdgcj03vmv9OAGXwpEy9gE8sLCdwmh4aW+K c6MV9xKu9mIYGi+CHbTtD7LeB9vIf1sXWOBQWwrd6Zi3PzEo5lgtnVg3DEKSwlpnSaG3g9 hIUmhyAJTquOWf4p11Q5jkwSFHB8jrI= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1780407467; 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=rPDZWrQrvp8j1kbdE+WXc6uZg5H54UA0eadxPXQn/+0=; b=y9CVPRB4UvydLH4kCwn/pFk4zeYqYR/GoYjnrVQ1zYkwmiQhgnMpY/EGzZ/L4/do38MfQ9 oteKt1T60uBDCECw== 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 EB605779A7; Tue, 2 Jun 2026 13:37:46 +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 6G+3LqrcHmoiQwAAD6G6ig (envelope-from ); Tue, 02 Jun 2026 13:37:46 +0000 From: Fabiano Rosas To: Peter Xu Cc: qemu-devel@nongnu.org, Paolo Bonzini , Mark Kanda , "Michael S . Tsirkin" , Markus Armbruster , Eric Blake , "Maciej S. Szmigiero" , Jason Wang , Ben Chaney , Vladimir Sementsov-Ogievskiy Subject: Re: [PATCH RFC 1/2] migration/vl: Allow set parameters with -incoming config:* In-Reply-To: References: <20260528212947.368132-1-peterx@redhat.com> <20260528212947.368132-2-peterx@redhat.com> <87pl2ftc12.fsf@suse.de> <87cxyetbc4.fsf@suse.de> Date: Tue, 02 Jun 2026 10:37:39 -0300 Message-ID: <87zf1d6p24.fsf@suse.de> MIME-Version: 1.0 Content-Type: text/plain X-Spamd-Result: default: False [-4.30 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; RCVD_VIA_SMTP_AUTH(0.00)[]; ARC_NA(0.00)[]; RCVD_TLS_ALL(0.00)[]; MISSING_XM_UA(0.00)[]; FUZZY_RATELIMITED(0.00)[rspamd.com]; 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)[]; TO_DN_SOME(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:helo,suse.de:mid] Received-SPF: pass client-ip=195.135.223.130; envelope-from=farosas@suse.de; helo=smtp-out1.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, 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: qemu development 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 Peter Xu writes: > On Fri, May 29, 2026 at 01:44:11PM -0300, Fabiano Rosas wrote: >> Peter Xu writes: >> >> > On Thu, May 28, 2026 at 07:16:57PM -0300, Fabiano Rosas wrote: >> >> Peter Xu writes: >> >> >> >> > QEMU doesn't yet have a good way to specify migration parameters so that >> >> > they can be available even during early stage of QEMU boots. It is because >> >> > the migration object (who owns the migration parameters) will only be >> >> > created after PHASE_LATE_BACKENDS_CREATED. It means anything before it >> >> > reading migration parameters is illegal. >> >> > >> >> > However, QEMU does have special use cases for such, namely only-migratable >> >> > flag, and cpr-transfer. Recently, we have one more possible user to read a >> >> > to-be-introduced new migration parameters during backend initialization >> >> > phase. We can introduce yet another global variable (or per-device >> >> > parameter) to bypass this limitation, but we can also seek for a generic >> >> > solution that we can setup migration parameters very early, even during >> >> > backend initializations. >> >> > >> >> > See this discussion for more details on the context of the problem: >> >> > >> >> > https://lore.kernel.org/r/ahdI7Vl5KraK566D@x1.local >> >> > >> >> > This patch wants to take the latter approach. >> >> > >> >> > As a start, introduce a new way to specify migration parameters in QEMU >> >> > boot commandline, as proposed in the above discussion: >> >> > >> >> > -incoming config:key1=value1,key2=value2,... >> >> > >> >> > When specified, QEMU will parse a string formatted MigrationParameters and >> >> > keep it. When migration object is created, it will apply all the settings >> >> > as initial value. >> >> > >> >> > Since the application of boot parameters will be after object_new() >> >> > completes, it means it happens after all machine compat properties or >> >> > -global settings (which should be done during instance_post_init()). >> >> > >> >> > So far, it's still only a way to specify parameters. All parameters are >> >> > not visible before migration object created, like before. Any parameter >> >> > that needs to be visible during boot will need to opt-in this feature. >> >> > Follow up patches will switch the current users to use this model. >> >> > >> >> > Signed-off-by: Peter Xu >> >> > --- >> >> > include/migration/misc.h | 5 ++++ >> >> > migration/migration.c | 54 ++++++++++++++++++++++++++++++++++++++++ >> >> > system/vl.c | 7 ++++++ >> >> > qemu-options.hx | 18 ++++++++++++-- >> >> > 4 files changed, 82 insertions(+), 2 deletions(-) >> >> > >> >> > diff --git a/include/migration/misc.h b/include/migration/misc.h >> >> > index 3159a5e53c..aff79b1380 100644 >> >> > --- a/include/migration/misc.h >> >> > +++ b/include/migration/misc.h >> >> > @@ -133,6 +133,11 @@ bool migrate_is_uri(const char *uri); >> >> > /* Parse @uri and return @channel, returning true on success */ >> >> > bool migrate_uri_parse(const char *uri, MigrationChannel **channel, >> >> > Error **errp); >> >> > +/* >> >> > + * Parse @config_str in form of "config:key1=value1,..." to initialize >> >> > + * migration parameters. >> >> > + */ >> >> > +bool migration_parameters_boot_parse(const char *config_str, Error **errp); >> >> > >> >> >> >> 'boot' is not the right word. Maybe 'early'? >> > >> > I am ok to switch to "early". Another option is.. "cmdline"? >> > >> >> Either is fine. >> >> >> >> >> > /* migration/multifd-device-state.c */ >> >> > typedef struct SaveCompletePrecopyThreadData { >> >> > diff --git a/migration/migration.c b/migration/migration.c >> >> > index 074d3f2c69..d918be7a44 100644 >> >> > --- a/migration/migration.c >> >> > +++ b/migration/migration.c >> >> > @@ -41,6 +41,7 @@ >> >> > #include "qapi/qapi-commands-migration.h" >> >> > #include "qapi/qapi-events-migration.h" >> >> > #include "qapi/qmp/qerror.h" >> >> > +#include "qapi/qobject-input-visitor.h" >> >> > #include "qobject/qnull.h" >> >> > #include "qemu/rcu.h" >> >> > #include "postcopy-ram.h" >> >> > @@ -94,6 +95,9 @@ enum mig_rp_message_type { >> >> > static MigrationState *current_migration; >> >> > static MigrationIncomingState *current_incoming; >> >> > >> >> > +/* Only used during boot, destroyed after migration object initialized */ >> >> > +static MigrationParameters *mig_boot_params; >> >> > + >> >> > static GSList *migration_blockers[MIG_MODE__MAX]; >> >> > >> >> > static bool migration_object_check(MigrationState *ms, Error **errp); >> >> > @@ -102,6 +106,45 @@ static bool stop_return_path_thread_on_source(MigrationState *s); >> >> > static void migration_release_dst_files(MigrationState *ms); >> >> > static void migration_completion_end(MigrationState *s); >> >> > >> >> > +bool migration_parameters_boot_parse(const char *config_str, Error **errp) >> >> > +{ >> >> > + Visitor *v; >> >> > + >> >> > + if (mig_boot_params) { >> >> > + error_setg(errp, "Only one -incoming config:* is allowed."); >> >> > + return false; >> >> > + } >> >> > + >> >> > + v = qobject_input_visitor_new_str(config_str, NULL, errp); >> >> > + if (!v) { >> >> > + goto fail; >> >> > + } >> >> > + >> >> > + if (!visit_type_MigrationParameters(v, NULL, &mig_boot_params, errp)) { >> >> > + goto fail; >> >> > + } >> >> > + >> >> > + visit_free(v); >> >> > + return true; >> >> > + >> >> > +fail: >> >> > + visit_free(v); >> >> > + return false; >> >> > +} >> >> > + >> >> > +static void migration_parameters_boot_apply(void) >> >> > +{ >> >> > + if (mig_boot_params) { >> >> > + /* >> >> > + * This can fail, because qobject visitor doesn't do sanity check >> >> > + * on values while parsing. It's not too late; we're still in boot >> >> > + * phase. >> >> > + */ >> >> > + qmp_migrate_set_parameters(mig_boot_params, &error_abort); >> >> > + g_clear_pointer(&mig_boot_params, qapi_free_MigrationParameters); >> >> > + } >> >> > +} >> >> > + >> >> > static void migration_downtime_start(MigrationState *s) >> >> > { >> >> > trace_vmstate_downtime_checkpoint("src-downtime-start"); >> >> > @@ -322,6 +365,17 @@ void migration_object_init(void) >> >> > >> >> > current_incoming->exit_on_error = INMIGRATE_DEFAULT_EXIT_ON_ERROR; >> >> > >> >> > + /* >> >> > + * Apply boot migration parameters in case the user specified some via >> >> > + * command line "-incoming config:*". NOTE: this will overwrite machine >> >> > + * type compat properties and -global settings! >> >> > + */ >> >> >> >> Hmm, but then it's exactly the same as -global migration.* ? Why do we >> >> need to extend -incoming? >> >> >> >> Also, I don't see how qmp_migrate_set_parameters can overwrite compat >> >> properties. They're not part of MigrationParameters. >> > >> > Some of this should have been mentioned in my other replies, let me know if >> > there's still concern over there after reading those. >> > >> >> The question about -global is non-sensical, forget about it. >> >> > In this case, after we set current_migration pointer compat properties are >> > applied, due to instance_post_init() happening within object_new(). >> > >> >> Yes, but migration_properties has two distinct sets of Properties, one >> contains only compat properties that match machine.c properties and the >> other has properties that go into MigrationParameters. I was under the >> impression that we never tied compat to parameters. >> >> The only machine compat property that is also a migration parameter I >> see is zero-page-detection. Maybe we shouldn't have done that. Now we >> can't decouple MigrationParameters from -global. Unless, of course we >> declare that from now on compat needs to be done with a new property >> that's not part of MigrationParameters; and duplicate >> zero-page-detection. > > I always treated migration parameters to be a subset of what we can apply > to compat properties in the past. > Good to know. > For example, -global almost works the same as compat properties and also at > the same time, currently both done in device_post_init(). > > In the future, if your series to convert caps to parameters work, then I > also want to add even more "parameters" (which used to be caps, like > postcopy preempt mode) into lists of machine compat properties, so e.g. we > can enable preempt mode by default. > > I hope that makes it useful, but if you still see some benefits of > splitting the two things (compat properties / parameters), let me know. I > may not have fully caught what you're visioning. > The problem I see is a long-standing one: MigrationParameters needs to be embedded into MigrationState because of -global (as both compat and debug feature). As long as that holds, we'll need workarounds such as having this extra early state. But let's not make this a problem to be solved in this series, please disconsider this discussion. Just to wrap my thoughts, for reference: What I want is a migration-owned MigrationParameters that we can do anything with, decoupled from whatever is needed to expose compat properties. There's two ways to achieve this: One is to declare parameters are separate from compat and drop the debug usage (what I suggested in my previous email). The other is to make MigrationState stop being a QOM object and instead make MigrationParameters itself be a QOM object. Then we could reference its members directly from qdev. >> >> >> >> >> > + migration_parameters_boot_apply(); >> >> > + >> >> > + /* >> >> > + * The boot parameters should have been verified already, but leave it >> >> > + * after applying boot parameters to do one check for everything. >> >> > + */ >> >> >> >> Will it get expensive? We do that for every QEMU start. >> > >> > Checking caps and parameters? Why expensive? >> > >> >> Just because we're putting more migration code in QEMU's startup >> path. Most QEMU invocations don't care about migration. Eventually, >> checking every parameter twice might have an impact. > > I would expect most QEMU invocations should care about migration, but > irrelevant of that.. I never expected these checks to be expensive. > Well, only a small subset of invocations will actually result in a migration. There's many uses of QEMU that don't require, or even cannot migrate. > postcopy_ram_supported_by_host() might be the heaviest, but it's > conditional and I still don't see it an issue. We also don't run any loop. > > What made you worry on this? > I don't know. The voices in my head. >> >> > Here I should have mentioned we must do one shot check here, because >> > sometimes there're illegal mixtures of "-incoming config*" and default >> > values only after they merged together. I'll update the comment for it, >> > IOW we must check here anyway. >> > >> >> Right. >> >> >> >> >> > migration_object_check(current_migration, &error_fatal); >> >> > >> >> > ram_mig_init(); >> >> > diff --git a/system/vl.c b/system/vl.c >> >> > index da36b2c6e1..49f5fa0c7b 100644 >> >> > --- a/system/vl.c >> >> > +++ b/system/vl.c >> >> > @@ -1838,6 +1838,13 @@ static void incoming_option_parse(const char *str) >> >> > >> >> > if (!strcmp(str, "defer")) { >> >> > channel = NULL; >> >> > + } else if (!strncmp(str, "config:", 7)) { >> >> > + /* >> >> > + * This is not a channel setup, but configuration to incoming >> >> > + * migration parameters to make them available during early boot. >> >> > + */ >> >> > + migration_parameters_boot_parse(str + 7, &error_fatal); >> >> > + return; >> >> > } else if (migrate_is_uri(str)) { >> >> > migrate_uri_parse(str, &channel, &error_fatal); >> >> > } else { >> >> > diff --git a/qemu-options.hx b/qemu-options.hx >> >> > index 96ae41f787..1fc92a409a 100644 >> >> > --- a/qemu-options.hx >> >> > +++ b/qemu-options.hx >> >> > @@ -5366,11 +5366,15 @@ DEF("incoming", HAS_ARG, QEMU_OPTION_incoming, \ >> >> > "-incoming \n" \ >> >> > " accept incoming migration on the migration channel\n" \ >> >> > "-incoming defer\n" \ >> >> > - " wait for the URI to be specified via migrate_incoming\n", >> >> > + " wait for the URI to be specified via migrate_incoming\n" >> >> > + "-incoming config:key1=value1,key2=value2,...\n" \ >> >> > + " specify migration parameters valid even during boot\n", >> >> > QEMU_ARCH_ALL) >> >> > SRST >> >> > + >> >> > The -incoming option specifies the migration channel for an incoming >> >> > -migration. It may be used multiple times to specify multiple >> >> > +migration, or can also be used to setup migration parameters for the >> >> > +incoming migration. It may be used multiple times to specify multiple >> >> > migration channel types. The channel type is specified in , >> >> > or is 'main' for all other forms of -incoming. If multiple -incoming >> >> > options are specified for a channel type, the last one takes precedence. >> >> > @@ -5411,6 +5415,16 @@ options are specified for a channel type, the last one takes precedence. >> >> > Wait for the URI to be specified via migrate\_incoming. The monitor >> >> > can be used to change settings (such as migration parameters) prior >> >> > to issuing the migrate\_incoming to allow the migration to begin. >> >> > + >> >> > +``-incoming config:key1=value1[,key2=value2,...]`` >> >> > + >> >> > + Specify migration parameters in QEMU commandlines, so that these >> >> >> >> command line >> > >> > Fixed. >> > >> >> >> >> > + parameters will be available even during very early boot of QEMU. >> >> > + They will be applied properly after QEMU boots and when the migration >> >> >> >> The "applied properly" part is implementation detail. >> > >> > True, I simplified it: >> > >> > ``-incoming config:key1=value1[,key2=value2,...]`` >> > >> > Specify migration parameters in QEMU command line, so that these >> > parameters will be available even during very early boot of QEMU. It >> > has similar effect as setting these parameters using QMP command >> > ``migrate-set-parameters`` or HMP command ``migrate_set_parameter``. >> > >> >> ack. >> >> >> >> >> > + core is initialized. From that POV, it has similar effect as setting >> >> > + these parameters using QMP command ``migrate-set-parameters`` or HMP >> >> > + command ``migrate_set_parameter``. >> >> > + >> >> > ERST >> >> > >> >> > DEF("only-migratable", 0, QEMU_OPTION_only_migratable, \ >> >> >>