[{"id":3675412,"web_url":"http://patchwork.ozlabs.org/comment/3675412/","msgid":"","list_archive_url":null,"date":"2026-04-09T17:13:20","subject":"Re: [PATCH 06/14] migration: Introduce stopcopy_bytes in\n save_query_pending()","submitter":{"id":89058,"url":"http://patchwork.ozlabs.org/api/people/89058/","name":"Juraj Marcin","email":"jmarcin@redhat.com"},"content":"On 2026-04-08 12:55, Peter Xu wrote:\n> Allow modules to report data that can only be migrated after VM is stopped.\n> \n> When this concept is introduced, we will need to account stopcopy size to\n> be part of pending_size as before.\n> \n> However, when there're data only can be migrated in stopcopy phase, it\n> means the old \"pending_size\" may not always be able to reach low enough to\n> kickoff an slow version of query sync.\n> \n> It used to be almost guaranteed to happen as all prior iterative modules\n> doesn't have stopcopy only data. VFIO may change that fact by having some\n> data that must be copied during stop phase.\n> \n> So we need to make sure QEMU will kickoff a synchronized version of query\n> pending when all precopy data is migrated. This might be important to VFIO\n> to keep making progress even if the downtime cannot yet be satisfied.\n> \n> So far, this patch should introduce no functional change, as no module yet\n> report stopcopy size.\n> \n> This paves way for VFIO to properly report its pending data sizes, which\n> will start to include stop-only data.\n> \n> Signed-off-by: Peter Xu \n> ---\n> include/migration/register.h | 7 +++++\n> migration/migration.c | 52 ++++++++++++++++++++++++++++++------\n> migration/savevm.c | 7 +++--\n> migration/trace-events | 2 +-\n> 4 files changed, 57 insertions(+), 11 deletions(-)\n> \n\nReviewed-by: Juraj Marcin ","headers":{"Return-Path":"","X-Original-To":"incoming@patchwork.ozlabs.org","Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (1024-bit key;\n unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256\n header.s=mimecast20190719 header.b=Z26yn3RN;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256\n header.s=google header.b=sv5O0ViQ;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=nongnu.org\n (client-ip=209.51.188.17; helo=lists.gnu.org;\n envelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org;\n receiver=patchwork.ozlabs.org)"],"Received":["from lists.gnu.org (lists1p.gnu.org [209.51.188.17])\n\t(using TLSv1.2 with cipher ECDHE-ECDSA-AES256-GCM-SHA384 (256/256 bits))\n\t(No client certificate requested)\n\tby legolas.ozlabs.org (Postfix) with ESMTPS id 4fs6376zZXz1yCv\n\tfor ; Fri, 10 Apr 2026 03:13:39 +1000 (AEST)","from localhost ([::1] helo=lists1p.gnu.org)\n\tby lists.gnu.org with esmtp (Exim 4.90_1)\n\t(envelope-from )\n\tid 1wAswd-00041P-A4; Thu, 09 Apr 2026 13:13:31 -0400","from eggs.gnu.org ([2001:470:142:3::10])\n by lists1p.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256)\n (Exim 4.90_1) (envelope-from )\n id 1wAswb-000419-DU\n for qemu-devel@nongnu.org; Thu, 09 Apr 2026 13:13:29 -0400","from us-smtp-delivery-124.mimecast.com ([170.10.129.124])\n by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256)\n (Exim 4.90_1) (envelope-from )\n id 1wAswZ-00006o-Of\n for qemu-devel@nongnu.org; Thu, 09 Apr 2026 13:13:29 -0400","from mail-wr1-f71.google.com (mail-wr1-f71.google.com\n [209.85.221.71]) by relay.mimecast.com with ESMTP with STARTTLS\n (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id\n us-mta-591-l2grSCPXMgqzhx9Dyu-G6w-1; Thu, 09 Apr 2026 13:13:25 -0400","by mail-wr1-f71.google.com with SMTP id\n ffacd0b85a97d-43d121c4271so753534f8f.3\n for ; Thu, 09 Apr 2026 10:13:25 -0700 (PDT)","from fedora (nat-88-212-17-233.antik.sk. 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Szmigiero\" , Daniel P\n\t=?utf-8?b?LiBCZXJyYW5nw6k=?= ,\n Zhiyi Guo , Prasad Pandit ,\n Avihai Horon , Kirti Wankhede ,\n\t=?utf-8?q?C=C3=A9dric?= Le Goater ,\n Fabiano Rosas , Joao Martins ,\n Markus Armbruster , Alex Williamson ","Subject":"Re: [PATCH 06/14] migration: Introduce stopcopy_bytes in\n save_query_pending()","Message-ID":"","References":"<20260408165559.157108-1-peterx@redhat.com>\n <20260408165559.157108-7-peterx@redhat.com>","MIME-Version":"1.0","Content-Type":"text/plain; charset=us-ascii","Content-Disposition":"inline","In-Reply-To":"<20260408165559.157108-7-peterx@redhat.com>","Received-SPF":"pass client-ip=170.10.129.124; envelope-from=jmarcin@redhat.com;\n helo=us-smtp-delivery-124.mimecast.com","X-Spam_score_int":"-25","X-Spam_score":"-2.6","X-Spam_bar":"--","X-Spam_report":"(-2.6 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.54,\n DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1,\n RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001,\n RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001,\n SPF_HELO_PASS=-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":",\n ","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n ","Errors-To":"qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org","Sender":"qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org"}},{"id":3675422,"web_url":"http://patchwork.ozlabs.org/comment/3675422/","msgid":"","list_archive_url":null,"date":"2026-04-09T17:36:51","subject":"Re: [PATCH 06/14] migration: Introduce stopcopy_bytes in\n save_query_pending()","submitter":{"id":89058,"url":"http://patchwork.ozlabs.org/api/people/89058/","name":"Juraj Marcin","email":"jmarcin@redhat.com"},"content":"Hi Peter,\n\nactually, I do have one question, see inline\n\nOn 2026-04-08 12:55, Peter Xu wrote:\n> Allow modules to report data that can only be migrated after VM is stopped.\n> \n> When this concept is introduced, we will need to account stopcopy size to\n> be part of pending_size as before.\n> \n> However, when there're data only can be migrated in stopcopy phase, it\n> means the old \"pending_size\" may not always be able to reach low enough to\n> kickoff an slow version of query sync.\n> \n> It used to be almost guaranteed to happen as all prior iterative modules\n> doesn't have stopcopy only data. VFIO may change that fact by having some\n> data that must be copied during stop phase.\n> \n> So we need to make sure QEMU will kickoff a synchronized version of query\n> pending when all precopy data is migrated. This might be important to VFIO\n> to keep making progress even if the downtime cannot yet be satisfied.\n> \n> So far, this patch should introduce no functional change, as no module yet\n> report stopcopy size.\n> \n> This paves way for VFIO to properly report its pending data sizes, which\n> will start to include stop-only data.\n> \n> Signed-off-by: Peter Xu \n> ---\n> include/migration/register.h | 7 +++++\n> migration/migration.c | 52 ++++++++++++++++++++++++++++++------\n> migration/savevm.c | 7 +++--\n> migration/trace-events | 2 +-\n> 4 files changed, 57 insertions(+), 11 deletions(-)\n> \n> diff --git a/include/migration/register.h b/include/migration/register.h\n> index aba3c9af2f..e822a2a59f 100644\n> --- a/include/migration/register.h\n> +++ b/include/migration/register.h\n> @@ -21,6 +21,13 @@ typedef struct MigPendingData {\n> uint64_t precopy_bytes;\n> /* Amount of pending bytes can be transferred in postcopy */\n> uint64_t postcopy_bytes;\n> + /* Amount of pending bytes can be transferred only in stopcopy */\n> + uint64_t stopcopy_bytes;\n> + /*\n> + * Total pending data, modules do not need to update this field, it\n> + * will be automatically calculated by migration core API.\n> + */\n> + uint64_t total_bytes;\n> } MigPendingData;\n> \n> /**\n> diff --git a/migration/migration.c b/migration/migration.c\n> index 68cfe2d3bf..bb17bd0e68 100644\n> --- a/migration/migration.c\n> +++ b/migration/migration.c\n> @@ -3198,6 +3198,44 @@ typedef enum {\n> MIG_ITERATE_BREAK, /* Break the loop */\n> } MigIterateState;\n> \n> +/* Are we ready to move to the next iteration phase? */\n> +static bool migration_iteration_next_ready(MigrationState *s,\n> + MigPendingData *pending)\n> +{\n> + /*\n> + * If the estimated values already suggest us to switchover, mark this\n> + * iteration finished, time to do a slow sync.\n> + */\n> + if (pending->total_bytes <= s->threshold_size) {\n> + return true;\n> + }\n> +\n> + /*\n> + * Since we may have modules reporting stop-only data, we also want to\n> + * re-query with slow mode if all precopy data is moved over. This\n> + * will also mark the current iteration done.\n> + *\n> + * This could happen when e.g. a module (like, VFIO) reports stopcopy\n> + * size too large so it will never yet satisfy the downtime with the\n> + * current setup (above check). Here, slow version of re-query helps\n> + * because we keep trying the best to move whatever we have.\n> + */\n> + if (pending->precopy_bytes == 0) {\n> + return true;\n> + }\n> +\n> + return false;\n> +}\n> +\n> +static void migration_iteration_go_next(MigPendingData *pending)\n> +{\n> + /*\n> + * Do a slow sync will achieve this. TODO: move RAM iteration code\n> + * into the core layer.\n> + */\n> + qemu_savevm_query_pending(pending, true);\n> +}\n> +\n> /*\n> * Return true if continue to the next iteration directly, false\n> * otherwise.\n> @@ -3209,12 +3247,10 @@ static MigIterateState migration_iteration_run(MigrationState *s)\n> s->state == MIGRATION_STATUS_POSTCOPY_ACTIVE);\n> bool can_switchover = migration_can_switchover(s);\n> MigPendingData pending = { };\n> - uint64_t pending_size;\n> bool complete_ready;\n> \n> /* Fast path - get the estimated amount of pending data */\n> qemu_savevm_query_pending(&pending, false);\n> - pending_size = pending.precopy_bytes + pending.postcopy_bytes;\n> \n> if (in_postcopy) {\n> /*\n> @@ -3222,7 +3258,7 @@ static MigIterateState migration_iteration_run(MigrationState *s)\n> * postcopy completion doesn't rely on can_switchover, because when\n> * POSTCOPY_ACTIVE it means switchover already happened.\n> */\n> - complete_ready = !pending_size;\n> + complete_ready = !pending.total_bytes;\n> if (s->state == MIGRATION_STATUS_POSTCOPY_DEVICE &&\n> (s->postcopy_package_loaded || complete_ready)) {\n> /*\n> @@ -3242,9 +3278,8 @@ static MigIterateState migration_iteration_run(MigrationState *s)\n> * postcopy started, so ESTIMATE should always match with EXACT\n> * during postcopy phase.\n> */\n> - if (pending_size <= s->threshold_size) {\n> - qemu_savevm_query_pending(&pending, true);\n> - pending_size = pending.precopy_bytes + pending.postcopy_bytes;\n> + if (migration_iteration_next_ready(s, &pending)) {\n> + migration_iteration_go_next(&pending);\n> }\n> \n> /* Should we switch to postcopy now? */\n> @@ -3264,11 +3299,12 @@ static MigIterateState migration_iteration_run(MigrationState *s)\n> * (2) Pending size is no more than the threshold specified\n> * (which was calculated from expected downtime)\n> */\n> - complete_ready = can_switchover && (pending_size <= s->threshold_size);\n> + complete_ready = can_switchover &&\n> + (pending.total_bytes <= s->threshold_size);\n\nshouldn't also the condition that triggers postcopy migration be updated?\nAs total_bytes is calculated as sum of all three\n(precopy_bytes + stopcopy_bytes + postcopy_bytes), this implies to me\nthat stopcopy_bytes is not subset of precopy_bytes and would also need\nto be migrated during switchover before postcopy.\n\nOnce this is resolved, then my Reviewed-by tag is valid, the patch looks\ngood to me otherwise.\n\nThanks!\n\n> }\n> \n> if (complete_ready) {\n> - trace_migration_thread_low_pending(pending_size);\n> + trace_migration_thread_low_pending(pending.total_bytes);\n> migration_completion(s);\n> return MIG_ITERATE_BREAK;\n> }\n> diff --git a/migration/savevm.c b/migration/savevm.c\n> index 397f602257..b75c311a95 100644\n> --- a/migration/savevm.c\n> +++ b/migration/savevm.c\n> @@ -1766,8 +1766,7 @@ void qemu_savevm_query_pending(MigPendingData *pending, bool exact)\n> {\n> SaveStateEntry *se;\n> \n> - pending->precopy_bytes = 0;\n> - pending->postcopy_bytes = 0;\n> + memset(pending, 0, sizeof(*pending));\n> \n> QTAILQ_FOREACH(se, &savevm_state.handlers, entry) {\n> if (!se->ops || !se->ops->save_query_pending) {\n> @@ -1779,7 +1778,11 @@ void qemu_savevm_query_pending(MigPendingData *pending, bool exact)\n> se->ops->save_query_pending(se->opaque, pending, exact);\n> }\n> \n> + pending->total_bytes = pending->precopy_bytes +\n> + pending->stopcopy_bytes + pending->postcopy_bytes;\n> +\n> trace_qemu_savevm_query_pending(exact, pending->precopy_bytes,\n> + pending->stopcopy_bytes,\n> pending->postcopy_bytes);\n> }\n> \n> diff --git a/migration/trace-events b/migration/trace-events\n> index f8995b8d0d..2f86ad448e 100644\n> --- a/migration/trace-events\n> +++ b/migration/trace-events\n> @@ -7,7 +7,7 @@ qemu_loadvm_state_section_partend(uint32_t section_id) \"%u\"\n> qemu_loadvm_state_post_main(int ret) \"%d\"\n> qemu_loadvm_state_section_startfull(uint32_t section_id, const char *idstr, uint32_t instance_id, uint32_t version_id) \"%u(%s) %u %u\"\n> qemu_savevm_send_packaged(void) \"\"\n> -qemu_savevm_query_pending(bool exact, uint64_t precopy, uint64_t postcopy) \"exact=%d, precopy=%\"PRIu64\", postcopy=%\"PRIu64\n> +qemu_savevm_query_pending(bool exact, uint64_t precopy, uint64_t stopcopy, uint64_t postcopy) \"exact=%d, precopy=%\"PRIu64\", stopcopy=%\"PRIu64\", postcopy=%\"PRIu64\n> loadvm_state_switchover_ack_needed(unsigned int switchover_ack_pending_num) \"Switchover ack pending num=%u\"\n> loadvm_state_setup(void) \"\"\n> loadvm_state_cleanup(void) \"\"\n> -- \n> 2.53.0\n>","headers":{"Return-Path":"","X-Original-To":"incoming@patchwork.ozlabs.org","Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (1024-bit key;\n unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256\n header.s=mimecast20190719 header.b=DshCbCH1;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256\n header.s=google header.b=YeK2VmNm;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=nongnu.org\n (client-ip=209.51.188.17; helo=lists.gnu.org;\n envelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org;\n receiver=patchwork.ozlabs.org)"],"Received":["from lists.gnu.org (lists1p.gnu.org [209.51.188.17])\n\t(using TLSv1.2 with cipher ECDHE-ECDSA-AES256-GCM-SHA384 (256/256 bits))\n\t(No client certificate requested)\n\tby legolas.ozlabs.org (Postfix) with ESMTPS id 4fs6b06TYgz1yHG\n\tfor ; Fri, 10 Apr 2026 03:37:47 +1000 (AEST)","from localhost ([::1] helo=lists1p.gnu.org)\n\tby lists.gnu.org with esmtp (Exim 4.90_1)\n\t(envelope-from )\n\tid 1wAtJO-0004MQ-Va; Thu, 09 Apr 2026 13:37:03 -0400","from eggs.gnu.org ([2001:470:142:3::10])\n by lists1p.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256)\n (Exim 4.90_1) (envelope-from )\n id 1wAtJN-0004M8-Og\n for qemu-devel@nongnu.org; Thu, 09 Apr 2026 13:37:01 -0400","from us-smtp-delivery-124.mimecast.com ([170.10.129.124])\n by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256)\n (Exim 4.90_1) (envelope-from )\n id 1wAtJL-0008F9-FG\n for qemu-devel@nongnu.org; Thu, 09 Apr 2026 13:37:01 -0400","from mail-wr1-f71.google.com (mail-wr1-f71.google.com\n [209.85.221.71]) by relay.mimecast.com with ESMTP with STARTTLS\n (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id\n us-mta-645-blyGG_uKOT24fx2hkcd2yA-1; Thu, 09 Apr 2026 13:36:56 -0400","by mail-wr1-f71.google.com with SMTP id\n ffacd0b85a97d-43d103e46c3so732066f8f.3\n for ; Thu, 09 Apr 2026 10:36:55 -0700 (PDT)","from fedora (nat-88-212-17-233.antik.sk. 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Szmigiero\" , Daniel P\n\t=?utf-8?b?LiBCZXJyYW5nw6k=?= ,\n Zhiyi Guo , Prasad Pandit ,\n Avihai Horon , Kirti Wankhede ,\n\t=?utf-8?q?C=C3=A9dric?= Le Goater ,\n Fabiano Rosas , Joao Martins ,\n Markus Armbruster , Alex Williamson ","Subject":"Re: [PATCH 06/14] migration: Introduce stopcopy_bytes in\n save_query_pending()","Message-ID":"","References":"<20260408165559.157108-1-peterx@redhat.com>\n <20260408165559.157108-7-peterx@redhat.com>","MIME-Version":"1.0","Content-Type":"text/plain; charset=us-ascii","Content-Disposition":"inline","In-Reply-To":"<20260408165559.157108-7-peterx@redhat.com>","Received-SPF":"pass client-ip=170.10.129.124; envelope-from=jmarcin@redhat.com;\n helo=us-smtp-delivery-124.mimecast.com","X-Spam_score_int":"-25","X-Spam_score":"-2.6","X-Spam_bar":"--","X-Spam_report":"(-2.6 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.54,\n DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1,\n RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001,\n RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001,\n SPF_HELO_PASS=-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":",\n ","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n ","Errors-To":"qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org","Sender":"qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org"}},{"id":3676637,"web_url":"http://patchwork.ozlabs.org/comment/3676637/","msgid":"<9e52a221-96f3-4c4c-9693-3235617d2a98@nvidia.com>","list_archive_url":null,"date":"2026-04-13T10:34:17","subject":"Re: [PATCH 06/14] migration: Introduce stopcopy_bytes in\n save_query_pending()","submitter":{"id":84049,"url":"http://patchwork.ozlabs.org/api/people/84049/","name":"Avihai Horon","email":"avihaih@nvidia.com"},"content":"On 4/8/2026 7:55 PM, Peter Xu wrote:\n> External email: Use caution opening links or attachments\n>\n>\n> Allow modules to report data that can only be migrated after VM is stopped.\n>\n> When this concept is introduced, we will need to account stopcopy size to\n> be part of pending_size as before.\n>\n> However, when there're data only can be migrated in stopcopy phase, it\n> means the old \"pending_size\" may not always be able to reach low enough to\n> kickoff an slow version of query sync.\n>\n> It used to be almost guaranteed to happen as all prior iterative modules\n> doesn't have stopcopy only data. VFIO may change that fact by having some\n> data that must be copied during stop phase.\n>\n> So we need to make sure QEMU will kickoff a synchronized version of query\n> pending when all precopy data is migrated. This might be important to VFIO\n> to keep making progress even if the downtime cannot yet be satisfied.\n>\n> So far, this patch should introduce no functional change, as no module yet\n> report stopcopy size.\n>\n> This paves way for VFIO to properly report its pending data sizes, which\n> will start to include stop-only data.\n>\n> Signed-off-by: Peter Xu \n> ---\n> include/migration/register.h | 7 +++++\n> migration/migration.c | 52 ++++++++++++++++++++++++++++++------\n> migration/savevm.c | 7 +++--\n> migration/trace-events | 2 +-\n> 4 files changed, 57 insertions(+), 11 deletions(-)\n>\n> diff --git a/include/migration/register.h b/include/migration/register.h\n> index aba3c9af2f..e822a2a59f 100644\n> --- a/include/migration/register.h\n> +++ b/include/migration/register.h\n> @@ -21,6 +21,13 @@ typedef struct MigPendingData {\n> uint64_t precopy_bytes;\n> /* Amount of pending bytes can be transferred in postcopy */\n> uint64_t postcopy_bytes;\n> + /* Amount of pending bytes can be transferred only in stopcopy */\n> + uint64_t stopcopy_bytes;\n> + /*\n> + * Total pending data, modules do not need to update this field, it\n> + * will be automatically calculated by migration core API.\n> + */\n> + uint64_t total_bytes;\n> } MigPendingData;\n>\n> /**\n> diff --git a/migration/migration.c b/migration/migration.c\n> index 68cfe2d3bf..bb17bd0e68 100644\n> --- a/migration/migration.c\n> +++ b/migration/migration.c\n> @@ -3198,6 +3198,44 @@ typedef enum {\n> MIG_ITERATE_BREAK, /* Break the loop */\n> } MigIterateState;\n>\n> +/* Are we ready to move to the next iteration phase? */\n> +static bool migration_iteration_next_ready(MigrationState *s,\n> + MigPendingData *pending)\n> +{\n> + /*\n> + * If the estimated values already suggest us to switchover, mark this\n> + * iteration finished, time to do a slow sync.\n> + */\n> + if (pending->total_bytes <= s->threshold_size) {\n> + return true;\n> + }\n> +\n> + /*\n> + * Since we may have modules reporting stop-only data, we also want to\n> + * re-query with slow mode if all precopy data is moved over. This\n> + * will also mark the current iteration done.\n> + *\n> + * This could happen when e.g. a module (like, VFIO) reports stopcopy\n> + * size too large so it will never yet satisfy the downtime with the\n> + * current setup (above check). Here, slow version of re-query helps\n> + * because we keep trying the best to move whatever we have.\n> + */\n> + if (pending->precopy_bytes == 0) {\n> + return true;\n> + }\n> +\n> + return false;\n> +}\n> +\n> +static void migration_iteration_go_next(MigPendingData *pending)\n> +{\n> + /*\n> + * Do a slow sync will achieve this. TODO: move RAM iteration code\n> + * into the core layer.\n> + */\n> + qemu_savevm_query_pending(pending, true);\n> +}\n> +\n> /*\n> * Return true if continue to the next iteration directly, false\n> * otherwise.\n> @@ -3209,12 +3247,10 @@ static MigIterateState migration_iteration_run(MigrationState *s)\n> s->state == MIGRATION_STATUS_POSTCOPY_ACTIVE);\n> bool can_switchover = migration_can_switchover(s);\n> MigPendingData pending = { };\n> - uint64_t pending_size;\n> bool complete_ready;\n>\n> /* Fast path - get the estimated amount of pending data */\n> qemu_savevm_query_pending(&pending, false);\n> - pending_size = pending.precopy_bytes + pending.postcopy_bytes;\n>\n> if (in_postcopy) {\n> /*\n> @@ -3222,7 +3258,7 @@ static MigIterateState migration_iteration_run(MigrationState *s)\n> * postcopy completion doesn't rely on can_switchover, because when\n> * POSTCOPY_ACTIVE it means switchover already happened.\n> */\n> - complete_ready = !pending_size;\n> + complete_ready = !pending.total_bytes;\n> if (s->state == MIGRATION_STATUS_POSTCOPY_DEVICE &&\n> (s->postcopy_package_loaded || complete_ready)) {\n> /*\n> @@ -3242,9 +3278,8 @@ static MigIterateState migration_iteration_run(MigrationState *s)\n> * postcopy started, so ESTIMATE should always match with EXACT\n> * during postcopy phase.\n> */\n> - if (pending_size <= s->threshold_size) {\n> - qemu_savevm_query_pending(&pending, true);\n> - pending_size = pending.precopy_bytes + pending.postcopy_bytes;\n> + if (migration_iteration_next_ready(s, &pending)) {\n> + migration_iteration_go_next(&pending);\n> }\n>\n> /* Should we switch to postcopy now? */\n\nI agree with Juraj, postcopy condition should also consider stopcopy_bytes.\n\n> @@ -3264,11 +3299,12 @@ static MigIterateState migration_iteration_run(MigrationState *s)\n> * (2) Pending size is no more than the threshold specified\n> * (which was calculated from expected downtime)\n> */\n> - complete_ready = can_switchover && (pending_size <= s->threshold_size);\n> + complete_ready = can_switchover &&\n> + (pending.total_bytes <= s->threshold_size);\n> }\n>\n> if (complete_ready) {\n> - trace_migration_thread_low_pending(pending_size);\n> + trace_migration_thread_low_pending(pending.total_bytes);\n> migration_completion(s);\n> return MIG_ITERATE_BREAK;\n> }\n> diff --git a/migration/savevm.c b/migration/savevm.c\n> index 397f602257..b75c311a95 100644\n> --- a/migration/savevm.c\n> +++ b/migration/savevm.c\n> @@ -1766,8 +1766,7 @@ void qemu_savevm_query_pending(MigPendingData *pending, bool exact)\n> {\n> SaveStateEntry *se;\n>\n> - pending->precopy_bytes = 0;\n> - pending->postcopy_bytes = 0;\n> + memset(pending, 0, sizeof(*pending));\n>\n> QTAILQ_FOREACH(se, &savevm_state.handlers, entry) {\n> if (!se->ops || !se->ops->save_query_pending) {\n> @@ -1779,7 +1778,11 @@ void qemu_savevm_query_pending(MigPendingData *pending, bool exact)\n> se->ops->save_query_pending(se->opaque, pending, exact);\n> }\n>\n> + pending->total_bytes = pending->precopy_bytes +\n> + pending->stopcopy_bytes + pending->postcopy_bytes;\n> +\n> trace_qemu_savevm_query_pending(exact, pending->precopy_bytes,\n> + pending->stopcopy_bytes,\n> pending->postcopy_bytes);\n\nWould it be convenient to also log pending->total_bytes?\n\nOther than that:\nReviewed-by: Avihai Horon \n\n> }\n>\n> diff --git a/migration/trace-events b/migration/trace-events\n> index f8995b8d0d..2f86ad448e 100644\n> --- a/migration/trace-events\n> +++ b/migration/trace-events\n> @@ -7,7 +7,7 @@ qemu_loadvm_state_section_partend(uint32_t section_id) \"%u\"\n> qemu_loadvm_state_post_main(int ret) \"%d\"\n> qemu_loadvm_state_section_startfull(uint32_t section_id, const char *idstr, uint32_t instance_id, uint32_t version_id) \"%u(%s) %u %u\"\n> qemu_savevm_send_packaged(void) \"\"\n> -qemu_savevm_query_pending(bool exact, uint64_t precopy, uint64_t postcopy) \"exact=%d, precopy=%\"PRIu64\", postcopy=%\"PRIu64\n> +qemu_savevm_query_pending(bool exact, uint64_t precopy, uint64_t stopcopy, uint64_t postcopy) \"exact=%d, precopy=%\"PRIu64\", stopcopy=%\"PRIu64\", postcopy=%\"PRIu64\n> loadvm_state_switchover_ack_needed(unsigned int switchover_ack_pending_num) \"Switchover ack pending num=%u\"\n> loadvm_state_setup(void) \"\"\n> loadvm_state_cleanup(void) \"\"\n> --\n> 2.53.0\n>","headers":{"Return-Path":"","X-Original-To":"incoming@patchwork.ozlabs.org","Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=Nvidia.com header.i=@Nvidia.com header.a=rsa-sha256\n header.s=selector2 header.b=DSG/2Nf4;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=nongnu.org\n (client-ip=209.51.188.17; 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Szmigiero\" , =?utf-8?q?Daniel_P_?=\n\t=?utf-8?q?=2E_Berrang=C3=A9?= ,\n Zhiyi Guo , Juraj Marcin ,\n Prasad Pandit , Kirti Wankhede ,\n\t=?utf-8?q?C=C3=A9dric_Le_Goater?= ,\n Fabiano Rosas , Joao Martins ,\n Markus Armbruster , Alex Williamson ","References":"<20260408165559.157108-1-peterx@redhat.com>\n <20260408165559.157108-7-peterx@redhat.com>","Content-Language":"en-US","From":"Avihai Horon ","In-Reply-To":"<20260408165559.157108-7-peterx@redhat.com>","Content-Type":"text/plain; charset=UTF-8; format=flowed","Content-Transfer-Encoding":"7bit","X-ClientProxiedBy":"FR4P281CA0242.DEUP281.PROD.OUTLOOK.COM\n (2603:10a6:d10:f5::20) To BL1PR12MB5063.namprd12.prod.outlook.com\n (2603:10b6:208:31a::11)","MIME-Version":"1.0","X-MS-PublicTrafficType":"Email","X-MS-TrafficTypeDiagnostic":"BL1PR12MB5063:EE_|SJ5PPFB332093D3:EE_","X-MS-Office365-Filtering-Correlation-Id":"5b253356-1b12-4cb6-9d7a-08de994839c8","X-MS-Exchange-SenderADCheck":"1","X-MS-Exchange-AntiSpam-Relay":"0","X-Microsoft-Antispam":"BCL:0;\n ARA:13230040|376014|7416014|1800799024|366016|56012099003|22082099003|18002099003;","X-Microsoft-Antispam-Message-Info":"\n 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","X-Forefront-Antispam-Report":"CIP:255.255.255.255; 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