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 18FC4CAC5B8 for ; Mon, 6 Oct 2025 13:25:26 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1v5lBi-00024w-Rf; Mon, 06 Oct 2025 09:23:38 -0400 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 1v5lBg-00024m-LU for qemu-devel@nongnu.org; Mon, 06 Oct 2025 09:23:36 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1v5lBa-0004Ap-II for qemu-devel@nongnu.org; Mon, 06 Oct 2025 09:23:35 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1759756999; h=from:from:reply-to:subject:subject: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=TIdmRzslPjPpbbg/p61Ee16OHYGAkAmrVz8zvtpoWG4=; b=cE1qFaK5j8tBfr7XT+U9lBji60hUWHX8dJr5eWnQRCdd+fcQlsOHnOXDIe9uiFNizX3iTW slegNTN2HpSNBmadW9Q3HusvVJKrGDl0vCG2pyW+Me5sOJo6kUXkVB+FMPlbvZz18jUrA0 45tlKZYTKdom/lv9ui2r7yXhnxqGT14= Received: from mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-528-pyiSKHLXMoWhQYyhL9rh1A-1; Mon, 06 Oct 2025 09:23:13 -0400 X-MC-Unique: pyiSKHLXMoWhQYyhL9rh1A-1 X-Mimecast-MFC-AGG-ID: pyiSKHLXMoWhQYyhL9rh1A_1759756992 Received: from mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.4]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 64B851800350; Mon, 6 Oct 2025 13:23:11 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.45.242.6]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 9E4553001FCA; Mon, 6 Oct 2025 13:23:09 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id D5D7A21E6A27; Mon, 06 Oct 2025 15:23:06 +0200 (CEST) From: Markus Armbruster To: Vladimir Sementsov-Ogievskiy Cc: mst@redhat.com, qemu-devel@nongnu.org, philmd@linaro.org, thuth@redhat.com, eblake@redhat.com, michael.roth@amd.com, farosas@suse.de, peterx@redhat.com, berrange@redhat.com, jasowang@redhat.com, steven.sistare@oracle.com, leiyang@redhat.com, davydov-max@yandex-team.ru, yc-core@yandex-team.ru Subject: Re: [PATCH v6 16/19] qapi: add interface for backend-transfer virtio-net/tap migration In-Reply-To: <20250923100110.70862-17-vsementsov@yandex-team.ru> (Vladimir Sementsov-Ogievskiy's message of "Tue, 23 Sep 2025 13:01:07 +0300") References: <20250923100110.70862-1-vsementsov@yandex-team.ru> <20250923100110.70862-17-vsementsov@yandex-team.ru> Date: Mon, 06 Oct 2025 15:23:06 +0200 Message-ID: <87v7kskvut.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 Received-SPF: pass client-ip=170.10.133.124; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -24 X-Spam_score: -2.5 X-Spam_bar: -- X-Spam_report: (-2.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.441, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, 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: 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 Vladimir Sementsov-Ogievskiy writes: > To migrate virtio-net TAP device backend (including open fds) locally, > user should simply set migration parameter > > backend-transfer = ["virtio-net-tap"] > > Why not simple boolean? To simplify migration to further versions, > when more devices will support backend-transfer migration. > > Alternatively, we may add per-device option to disable backend-transfer > migration, but still: > > 1. It's more comfortable to set same capabilities/parameters on both > source and target QEMU, than care about each device. > > 2. To not break the design, that machine-type + device options + > migration capabilities and parameters are fully define the resulting > migration stream. We'll break this if add in future more > backend-transfer support in devices under same backend-transfer=true > parameter. > > Signed-off-by: Vladimir Sementsov-Ogievskiy > --- > include/qapi/util.h | 17 ++++++++++++++++ > migration/options.c | 32 ++++++++++++++++++++++++++++++ > migration/options.h | 2 ++ > qapi/migration.json | 47 ++++++++++++++++++++++++++++++++++++--------- > 4 files changed, 89 insertions(+), 9 deletions(-) > > diff --git a/include/qapi/util.h b/include/qapi/util.h > index 29bc4eb865..b953402416 100644 > --- a/include/qapi/util.h > +++ b/include/qapi/util.h > @@ -69,4 +69,21 @@ int parse_qapi_name(const char *name, bool complete); > _len; \ > }) > > +/* > + * For any GenericList @list, return true if it contains specified > + * element. > + */ > +#define QAPI_LIST_CONTAINS(list, el) \ > + ({ \ > + bool _found = false; \ > + typeof_strip_qual(list) _tail; \ > + for (_tail = list; _tail != NULL; _tail = _tail->next) { \ > + if (_tail->value == el) { \ > + _found = true; \ > + break; \ > + } \ > + } \ > + _found; \ > + }) > + Not a fan of lengthy macros. There's a single use below: migrate_virtio_net_tap(). I can't see potential uses for such a search in existing code. Open-code it in migrate_virtio_net_tap()? > #endif > diff --git a/migration/options.c b/migration/options.c > index 4e923a2e07..137ca2147e 100644 > --- a/migration/options.c > +++ b/migration/options.c > @@ -13,6 +13,7 @@ > > #include "qemu/osdep.h" > #include "qemu/error-report.h" > +#include "qapi/util.h" > #include "exec/target_page.h" > #include "qapi/clone-visitor.h" > #include "qapi/error.h" > @@ -262,6 +263,14 @@ bool migrate_mapped_ram(void) > return s->capabilities[MIGRATION_CAPABILITY_MAPPED_RAM]; > } > > +bool migrate_virtio_net_tap(void) > +{ > + MigrationState *s = migrate_get_current(); > + > + return QAPI_LIST_CONTAINS(s->parameters.backend_transfer, > + BACKEND_TRANSFER_VIRTIO_NET_TAP); > +} > + > bool migrate_ignore_shared(void) > { > MigrationState *s = migrate_get_current(); > @@ -960,6 +969,12 @@ MigrationParameters *qmp_query_migrate_parameters(Error **errp) > params->has_direct_io = true; > params->direct_io = s->parameters.direct_io; > > + if (s->parameters.backend_transfer) { > + params->has_backend_transfer = true; > + params->backend_transfer = QAPI_CLONE(BackendTransferList, > + s->parameters.backend_transfer); > + } > + > return params; > } > > @@ -993,6 +1008,7 @@ void migrate_params_init(MigrationParameters *params) > params->has_mode = true; > params->has_zero_page_detection = true; > params->has_direct_io = true; > + params->has_backend_transfer = true; > } > > /* > @@ -1179,6 +1195,11 @@ bool migrate_params_check(MigrationParameters *params, Error **errp) > return false; > } > > + if (params->has_backend_transfer) { > + error_setg(errp, "Not implemented"); > + return false; > + } > + This goes away in the next patch. Fine, but mentioning the gap in the commit message can save reviewer a bit of work. > return true; > } > > @@ -1297,6 +1318,10 @@ static void migrate_params_test_apply(MigrateSetParameters *params, > if (params->has_direct_io) { > dest->direct_io = params->direct_io; > } > + > + if (params->has_backend_transfer) { > + dest->backend_transfer = params->backend_transfer; > + } > } > > static void migrate_params_apply(MigrateSetParameters *params, Error **errp) > @@ -1429,6 +1454,13 @@ static void migrate_params_apply(MigrateSetParameters *params, Error **errp) > if (params->has_direct_io) { > s->parameters.direct_io = params->direct_io; > } > + > + if (params->has_backend_transfer) { > + qapi_free_BackendTransferList(s->parameters.backend_transfer); > + > + s->parameters.backend_transfer = QAPI_CLONE(BackendTransferList, > + params->backend_transfer); > + } > } > > void qmp_migrate_set_parameters(MigrateSetParameters *params, Error **errp) > diff --git a/migration/options.h b/migration/options.h > index 82d839709e..55c0345433 100644 > --- a/migration/options.h > +++ b/migration/options.h > @@ -87,6 +87,8 @@ const char *migrate_tls_hostname(void); > uint64_t migrate_xbzrle_cache_size(void); > ZeroPageDetection migrate_zero_page_detection(void); > > +bool migrate_virtio_net_tap(void); > + > /* parameters helpers */ > > bool migrate_params_check(MigrationParameters *params, Error **errp); > diff --git a/qapi/migration.json b/qapi/migration.json > index 2387c21e9c..e39785dc07 100644 > --- a/qapi/migration.json > +++ b/qapi/migration.json > @@ -747,6 +747,18 @@ > '*transform': 'BitmapMigrationBitmapAliasTransform' > } } > > +## > +# @BackendTransfer: > +# > +# @virtio-net-tap: Enable backend-transfer migration for virtio-net/tap. When > +# enabled, TAP fds and all related state is passed to target QEMU through > +# migration channel (which should be unix socket). Suggest "are passed to the destination in the migration channel" and "should be a UNIX domain socket". docs/devel/qapi-code-gen.rst: For legibility, wrap text paragraphs so every line is at most 70 characters long. Separate sentences with two spaces. > +# > +# Since: 10.2 > +## > +{ 'enum': 'BackendTransfer', > + 'data': [ 'virtio-net-tap' ] } > + > ## > # @BitmapMigrationNodeAlias: > # > @@ -924,10 +936,14 @@ > # only has effect if the @mapped-ram capability is enabled. > # (Since 9.1) > # > +# @backend-transfer: List of targets to enable backend-transfer > +# migration for. This requires migration channel to be a unix > +# socket (to pass fds through). (Since 10.2) Elsewhere, we describe the same restriction like this: This CPR channel must support # file descriptor transfer with SCM_RIGHTS, i.e. it must be a # UNIX domain socket. > +# > # Features: > # > -# @unstable: Members @x-checkpoint-delay and > -# @x-vcpu-dirty-limit-period are experimental. > +# @unstable: Members @x-checkpoint-delay, > +# @x-vcpu-dirty-limit-period and @backend-transfer are experimental. List members in alphabetical order, please. > # > # Since: 2.4 > ## > @@ -950,7 +966,8 @@ > 'vcpu-dirty-limit', > 'mode', > 'zero-page-detection', > - 'direct-io'] } > + 'direct-io', > + 'backend-transfer' ] } Forgot feature 'unstable'? > > ## > # @MigrateSetParameters: > @@ -1105,10 +1122,14 @@ > # only has effect if the @mapped-ram capability is enabled. > # (Since 9.1) > # > +# @backend-transfer: List of targets to enable backend-transfer > +# migration for. This requires migration channel to be a unix > +# socket (to pass fds through). (Since 10.2) > +# > # Features: > # > -# @unstable: Members @x-checkpoint-delay and > -# @x-vcpu-dirty-limit-period are experimental. > +# @unstable: Members @x-checkpoint-delay, > +# @x-vcpu-dirty-limit-period and @backend-transfer are experimental. > # > # TODO: either fuse back into `MigrationParameters`, or make > # `MigrationParameters` members mandatory > @@ -1146,7 +1167,9 @@ > '*vcpu-dirty-limit': 'uint64', > '*mode': 'MigMode', > '*zero-page-detection': 'ZeroPageDetection', > - '*direct-io': 'bool' } } > + '*direct-io': 'bool', > + '*backend-transfer': { 'type': [ 'BackendTransfer' ], > + 'features': [ 'unstable' ] } } } > > ## > # @migrate-set-parameters: > @@ -1315,10 +1338,14 @@ > # only has effect if the @mapped-ram capability is enabled. > # (Since 9.1) > # > +# @backend-transfer: List of targets to enable backend-transfer > +# migration for. This requires migration channel to be a unix > +# socket (to pass fds through). (Since 10.2) > +# > # Features: > # > -# @unstable: Members @x-checkpoint-delay and > -# @x-vcpu-dirty-limit-period are experimental. > +# @unstable: Members @x-checkpoint-delay, > +# @x-vcpu-dirty-limit-period and @backend-transfer are experimental. > # > # Since: 2.4 > ## > @@ -1353,7 +1380,9 @@ > '*vcpu-dirty-limit': 'uint64', > '*mode': 'MigMode', > '*zero-page-detection': 'ZeroPageDetection', > - '*direct-io': 'bool' } } > + '*direct-io': 'bool', > + '*backend-transfer': { 'type': [ 'BackendTransfer' ], > + 'features': [ 'unstable' ] } } } > > ## > # @query-migrate-parameters: