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 0FE31C77B73 for ; Tue, 30 May 2023 09:59:15 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1q3w7q-00035x-4S; Tue, 30 May 2023 05:58:46 -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 1q3w7o-00035k-Qe for qemu-devel@nongnu.org; Tue, 30 May 2023 05:58:44 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1q3w7m-0005d8-Lz for qemu-devel@nongnu.org; Tue, 30 May 2023 05:58:44 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1685440721; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=EhYUXgIymTmL+j0YD1YHBDo0tqrQE3RzLvzPPiNNWvU=; b=dxy85VBUILmOKENok0wlJ1Wr92RqIHAnzGEeveTip59r9ob3iQcemHEibUaHobTR3fur1j HlnINAk0rDLh8Tfm9Z+VEBJc96WZIw0Q/8pZXhk7s/+Q6AjxWD65RBcXBRM3G5oWtZGEAZ Uql5iBJpX1BgtA3beZGH9yVlNe24Vcg= Received: from mail-wm1-f72.google.com (mail-wm1-f72.google.com [209.85.128.72]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-399-i-GeYDQWMiKbpUgsuMeL3Q-1; Tue, 30 May 2023 05:58:40 -0400 X-MC-Unique: i-GeYDQWMiKbpUgsuMeL3Q-1 Received: by mail-wm1-f72.google.com with SMTP id 5b1f17b1804b1-3f60f085cd2so15921965e9.0 for ; Tue, 30 May 2023 02:58:39 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1685440719; x=1688032719; h=content-transfer-encoding:in-reply-to:from:references:cc:to :content-language:subject:user-agent:mime-version:date:message-id :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=EhYUXgIymTmL+j0YD1YHBDo0tqrQE3RzLvzPPiNNWvU=; b=ivzIxKjdFnYnRgr6OCApJhuyIook4ct53ditipVAiHGatbdE75IreXXpWX3GkUx03F yzYpQyV0qBqKKUQOkVx/VktmWYI8Kx6Em/drpLHfHmfLCIimWj0aF1hEQRx6zHFU5m87 qAH3Zic0eKZUAKhRVSSrmc4UiqBmimMwdx691uNPhEdVjn2G7bH+2SSVpyin8NcPZY/Z yjjGAmNkCvzEtgoqABDobxG+Xc5b9awPZLrRwd/zvFh4FIOCgbT9185CguX2ePewX/3g W2h2ytJmZyvWMq8xIyBQIpit3XO9zwTyybws9FzApgiXDkBp0796IvArXb9TqWu2c1yn QD9g== X-Gm-Message-State: AC+VfDzwdWVmSW1ye7BQt4HtOhF82tdeRQSvLRQW+Cx3ilOHMbeKsyQT mIxTTM+/Uxayd6+jC0noTZNT2zs0i4AXsgH9bECPWTjXTFBf7SbjFWBD92+Dy96fHtjczVrNNjL rQ1r38js84AaaHME= X-Received: by 2002:a05:600c:2252:b0:3f6:8af:414 with SMTP id a18-20020a05600c225200b003f608af0414mr1267906wmm.30.1685440718916; Tue, 30 May 2023 02:58:38 -0700 (PDT) X-Google-Smtp-Source: ACHHUZ7WXNH2PhbAuUeDJax0Xq580LD278vETEQ+F0J9mMf9oFyJLPpFTeDMMtkFb5Va6J2lR2NGzQ== X-Received: by 2002:a05:600c:2252:b0:3f6:8af:414 with SMTP id a18-20020a05600c225200b003f608af0414mr1267884wmm.30.1685440718594; Tue, 30 May 2023 02:58:38 -0700 (PDT) Received: from ?IPV6:2a01:e0a:280:24f0:eb4a:c9d8:c8bb:c0b0? ([2a01:e0a:280:24f0:eb4a:c9d8:c8bb:c0b0]) by smtp.gmail.com with ESMTPSA id o11-20020a05600c378b00b003f195d540d9sm20553665wmr.14.2023.05.30.02.58.37 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 30 May 2023 02:58:38 -0700 (PDT) Message-ID: Date: Tue, 30 May 2023 11:58:36 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.10.0 Subject: Re: [PATCH v4 9/9] vfio/migration: Add support for switchover ack capability Content-Language: en-US To: Avihai Horon , qemu-devel@nongnu.org Cc: Alex Williamson , Eduardo Habkost , Marcel Apfelbaum , =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= , Yanan Wang , Juan Quintela , Peter Xu , Leonardo Bras , Eric Blake , Markus Armbruster , Thomas Huth , Laurent Vivier , Paolo Bonzini , Yishai Hadas , Jason Gunthorpe , Maor Gottlieb , Kirti Wankhede , Tarun Gupta , Joao Martins References: <20230528140652.8693-1-avihaih@nvidia.com> <20230528140652.8693-10-avihaih@nvidia.com> From: =?UTF-8?Q?C=c3=a9dric_Le_Goater?= In-Reply-To: <20230528140652.8693-10-avihaih@nvidia.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=170.10.129.124; envelope-from=clg@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -23 X-Spam_score: -2.4 X-Spam_bar: -- X-Spam_report: (-2.4 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.16, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.091, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 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 On 5/28/23 16:06, Avihai Horon wrote: > Loading of a VFIO device's data can take a substantial amount of time as > the device may need to allocate resources, prepare internal data > structures, etc. This can increase migration downtime, especially for > VFIO devices with a lot of resources. > > To solve this, VFIO migration uAPI defines "initial bytes" as part of > its precopy data stream. Initial bytes can be used in various ways to > improve VFIO migration performance. For example, it can be used to > transfer device metadata to pre-allocate resources in the destination. > However, for this to work we need to make sure that all initial bytes > are sent and loaded in the destination before the source VM is stopped. > > Use migration switchover ack capability to make sure a VFIO device's > initial bytes are sent and loaded in the destination before the source > stops the VM and attempts to complete the migration. > This can significantly reduce migration downtime for some devices. > > As precopy support and precopy initial bytes support come together in > VFIO migration, use x-allow-pre-copy device property to control usage of > this feature as well. > > Signed-off-by: Avihai Horon > --- > docs/devel/vfio-migration.rst | 10 ++++++++ > include/hw/vfio/vfio-common.h | 2 ++ > hw/vfio/migration.c | 48 ++++++++++++++++++++++++++++++++++- > 3 files changed, 59 insertions(+), 1 deletion(-) > > diff --git a/docs/devel/vfio-migration.rst b/docs/devel/vfio-migration.rst > index e896b2a673..b433cb5bb2 100644 > --- a/docs/devel/vfio-migration.rst > +++ b/docs/devel/vfio-migration.rst > @@ -16,6 +16,13 @@ helps to reduce the total downtime of the VM. VFIO devices opt-in to pre-copy > support by reporting the VFIO_MIGRATION_PRE_COPY flag in the > VFIO_DEVICE_FEATURE_MIGRATION ioctl. > > +When pre-copy is supported, it's possible to further reduce downtime by > +enabling "switchover-ack" migration capability. > +VFIO migration uAPI defines "initial bytes" as part of its pre-copy data stream > +and recommends that the initial bytes are sent and loaded in the destination > +before stopping the source VM. Enabling this migration capability will > +guarantee that and thus, can potentially reduce downtime even further. > + > Note that currently VFIO migration is supported only for a single device. This > is due to VFIO migration's lack of P2P support. However, P2P support is planned > to be added later on. > @@ -45,6 +52,9 @@ VFIO implements the device hooks for the iterative approach as follows: > * A ``save_live_iterate`` function that reads the VFIO device's data from the > vendor driver during iterative pre-copy phase. > > +* A ``switchover_ack_needed`` function that checks if the VFIO device uses > + "switchover-ack" migration capability when this capability is enabled. > + > * A ``save_state`` function to save the device config space if it is present. > > * A ``save_live_complete_precopy`` function that sets the VFIO device in > diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h > index a53ecbe2e0..ad0562c8b7 100644 > --- a/include/hw/vfio/vfio-common.h > +++ b/include/hw/vfio/vfio-common.h > @@ -69,6 +69,8 @@ typedef struct VFIOMigration { > uint64_t mig_flags; > uint64_t precopy_init_size; > uint64_t precopy_dirty_size; > + bool switchover_ack_needed; Do we really need the 'switchover_ack_needed' bool ? It seems that each time it is used in a routine it could be computed locally with migrate_switchover_ack() and vfio_precopy_supported(). This would simplify the code a bit more. Thanks, C. > + bool initial_data_sent; > } VFIOMigration; > > typedef struct VFIOAddressSpace { > diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c > index cb6923ed3f..ede29ffb5c 100644 > --- a/hw/vfio/migration.c > +++ b/hw/vfio/migration.c > @@ -18,6 +18,8 @@ > #include "sysemu/runstate.h" > #include "hw/vfio/vfio-common.h" > #include "migration/migration.h" > +#include "migration/options.h" > +#include "migration/savevm.h" > #include "migration/vmstate.h" > #include "migration/qemu-file.h" > #include "migration/register.h" > @@ -45,6 +47,7 @@ > #define VFIO_MIG_FLAG_DEV_CONFIG_STATE (0xffffffffef100002ULL) > #define VFIO_MIG_FLAG_DEV_SETUP_STATE (0xffffffffef100003ULL) > #define VFIO_MIG_FLAG_DEV_DATA_STATE (0xffffffffef100004ULL) > +#define VFIO_MIG_FLAG_DEV_INIT_DATA_SENT (0xffffffffef100005ULL) > > /* > * This is an arbitrary size based on migration of mlx5 devices, where typically > @@ -218,6 +221,7 @@ static void vfio_migration_cleanup(VFIODevice *vbasedev) > > close(migration->data_fd); > migration->data_fd = -1; > + migration->switchover_ack_needed = false; > } > > static int vfio_query_stop_copy_size(VFIODevice *vbasedev, > @@ -350,6 +354,10 @@ static int vfio_save_setup(QEMUFile *f, void *opaque) > if (vfio_precopy_supported(vbasedev)) { > int ret; > > + if (migrate_switchover_ack()) { > + migration->switchover_ack_needed = true; > + } > + > switch (migration->device_state) { > case VFIO_DEVICE_STATE_RUNNING: > ret = vfio_migration_set_state(vbasedev, VFIO_DEVICE_STATE_PRE_COPY, > @@ -385,6 +393,7 @@ static void vfio_save_cleanup(void *opaque) > migration->data_buffer = NULL; > migration->precopy_init_size = 0; > migration->precopy_dirty_size = 0; > + migration->initial_data_sent = false; > vfio_migration_cleanup(vbasedev); > trace_vfio_save_cleanup(vbasedev->name); > } > @@ -458,10 +467,17 @@ static int vfio_save_iterate(QEMUFile *f, void *opaque) > if (data_size < 0) { > return data_size; > } > - qemu_put_be64(f, VFIO_MIG_FLAG_END_OF_STATE); > > vfio_update_estimated_pending_data(migration, data_size); > > + if (migration->switchover_ack_needed && !migration->precopy_init_size && > + !migration->initial_data_sent) { > + qemu_put_be64(f, VFIO_MIG_FLAG_DEV_INIT_DATA_SENT); > + migration->initial_data_sent = true; > + } else { > + qemu_put_be64(f, VFIO_MIG_FLAG_END_OF_STATE); > + } > + > trace_vfio_save_iterate(vbasedev->name, migration->precopy_init_size, > migration->precopy_dirty_size); > > @@ -526,6 +542,10 @@ static int vfio_load_setup(QEMUFile *f, void *opaque) > { > VFIODevice *vbasedev = opaque; > > + if (migrate_switchover_ack() && vfio_precopy_supported(vbasedev)) { > + vbasedev->migration->switchover_ack_needed = true; > + } > + > return vfio_migration_set_state(vbasedev, VFIO_DEVICE_STATE_RESUMING, > vbasedev->migration->device_state); > } > @@ -580,6 +600,23 @@ static int vfio_load_state(QEMUFile *f, void *opaque, int version_id) > } > break; > } > + case VFIO_MIG_FLAG_DEV_INIT_DATA_SENT: > + { > + if (!vbasedev->migration->switchover_ack_needed) { > + error_report("%s: Received INIT_DATA_SENT but switchover ack " > + "is not needed", vbasedev->name); > + return -EINVAL; > + } > + > + ret = qemu_loadvm_approve_switchover(); > + if (ret) { > + error_report( > + "%s: qemu_loadvm_approve_switchover failed, err=%d (%s)", > + vbasedev->name, ret, strerror(-ret)); > + } > + > + return ret; > + } > default: > error_report("%s: Unknown tag 0x%"PRIx64, vbasedev->name, data); > return -EINVAL; > @@ -594,6 +631,14 @@ static int vfio_load_state(QEMUFile *f, void *opaque, int version_id) > return ret; > } > > +static bool vfio_switchover_ack_needed(void *opaque) > +{ > + VFIODevice *vbasedev = opaque; > + VFIOMigration *migration = vbasedev->migration; > + > + return migration->switchover_ack_needed; > +} > + > static const SaveVMHandlers savevm_vfio_handlers = { > .save_setup = vfio_save_setup, > .save_cleanup = vfio_save_cleanup, > @@ -606,6 +651,7 @@ static const SaveVMHandlers savevm_vfio_handlers = { > .load_setup = vfio_load_setup, > .load_cleanup = vfio_load_cleanup, > .load_state = vfio_load_state, > + .switchover_ack_needed = vfio_switchover_ack_needed, > }; > > /* ---------------------------------------------------------------------- */