From nobody Sat Apr 11 18:38:00 2026 Delivered-To: importer@patchew.org Authentication-Results: mx.zohomail.com; dkim=pass; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=pass(p=quarantine dis=none) header.from=redhat.com ARC-Seal: i=1; a=rsa-sha256; t=1775677156; cv=none; d=zohomail.com; s=zohoarc; b=e5GvNL2urVOfixxP6xv2llmNJ/2h9TWBVJeZmkoRUp1gO4YeES3A7wzhpLnaYE8QeXuv+/+UvecPADwAD5m/KMOCO47y+pcAHXf6dj2C29GRThYZdoTf2+/OwFG5l+3B1M4+ytljZI08BmN0LNc/hq85fQnBHIKppMkQ0eLHqp0= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1775677156; h=Content-Transfer-Encoding:Cc:Cc:Date:Date:From:From:In-Reply-To:List-Subscribe:List-Post:List-Id:List-Archive:List-Help:List-Unsubscribe:MIME-Version:Message-ID:References:Sender:Subject:Subject:To:To:Message-Id:Reply-To; bh=O0kLvM+Gei19WRwCTbcZcMBvammqKpOVcflr0Var+P0=; b=aLmm4+mTM5nnqE31ZatKLdoPKKllpLXpRiYIiIJgKVdTHP8STDqC7+m7AEOwyTgEWplfXZRwjlxfbtXiKaw9bqWnoBhYEkOqBv3s6JBDXl6Z4GfHgE7Br41Ebzbeu6VsFMtz46pZZwLNxPFm0WkjdYQR7+x/LLrXIRUF58EqYwk= ARC-Authentication-Results: i=1; mx.zohomail.com; dkim=pass; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=pass header.from= (p=quarantine dis=none) Return-Path: Received: from lists.gnu.org (lists1p.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1775677156769382.60538815443533; Wed, 8 Apr 2026 12:39:16 -0700 (PDT) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1wAYc1-0004T5-Kj; Wed, 08 Apr 2026 15:30:53 -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 1wAYA0-0000eP-6E for qemu-devel@nongnu.org; Wed, 08 Apr 2026 15:01:56 -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 1wAWCH-00027V-Jm for qemu-devel@nongnu.org; Wed, 08 Apr 2026 12:56:11 -0400 Received: from mail-qt1-f197.google.com (mail-qt1-f197.google.com [209.85.160.197]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-369-6u8ACfTEOH6qaFTmWXXM1w-1; Wed, 08 Apr 2026 12:56:07 -0400 Received: by mail-qt1-f197.google.com with SMTP id d75a77b69052e-50b52a2d70cso3165141cf.3 for ; Wed, 08 Apr 2026 09:56:07 -0700 (PDT) Received: from x1.com ([142.189.10.167]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-50d712c2617sm130491901cf.31.2026.04.08.09.56.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 08 Apr 2026 09:56:05 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1775667369; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=O0kLvM+Gei19WRwCTbcZcMBvammqKpOVcflr0Var+P0=; b=TOxsC97SY+/CqdyxPyWbwwTN2iXkEGi+4+viWa8QvhthtNsuvMpO4CpFqnMNFhiiC4gJoP QYB2R/BKQqjocs/EjXRU+hngRvt3xxCB/onLOS8njRgAXI6/pDKZFLhalc6E/Bl9cOjdXr 0U0MGfuolKzkMi5M9ua7IKgg93vmC5Q= X-MC-Unique: 6u8ACfTEOH6qaFTmWXXM1w-1 X-Mimecast-MFC-AGG-ID: 6u8ACfTEOH6qaFTmWXXM1w_1775667367 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=google; t=1775667366; x=1776272166; darn=nongnu.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=O0kLvM+Gei19WRwCTbcZcMBvammqKpOVcflr0Var+P0=; b=DDZlKDEgEq03sIhsAAWpseF9NY3sC/xZQ+CpfoyUMKyjp379DeuiqfpBIZAY5J1CPJ jI1Jf8ugh+QMjxzbHxPRLxA4edDVyFlvlmr+kbMrpvo4im9SvcIi+oN5iAEmsJl0d4kV BX6joadC9Zq2ZjIaBWMN19qhVNbasIUOZuTHLaOz54ImQ22z31DaG5synaMBlmKspEpN Uzu6qCykXud3whBP5RxOOqSO6SlVQSDPJM8jT2QQIq1ErXEXbe15RPkjhU0RstYfviqs lIxW6rHe9E+WFvs/c+6867t8E6VwLMqLeIZFzWxySljmkvLztTPHpK3cUoHTg1hihS9u JgLQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1775667366; x=1776272166; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to; bh=O0kLvM+Gei19WRwCTbcZcMBvammqKpOVcflr0Var+P0=; b=p++CQpcXg2T0FbtX6mztUBvKeax2aORg/9eQKfUzXIp0lh0EimVyQWUfDuA1Ly6g3B ZGk9ZnyViZ5zuTsCqxS7NhUb8zW5eORBa1yjVLpfrldVJNkQfHVC+Kx+ynQrGYizbAAG w6PrB6sBmfcWBETgKTMKGAK2X2LOOADnLbtDFWWjNk9DXbsAv3k/SOQhniEoIvVzrppc gCxD/wATSfZIj8lbhkNDWLPW+JCJUKmelCxY0Bp8IbmxRaSE1r0zZYa6SxfYFWPzczXo Xp6jRJuGJ+zAhOzBae5NgcqvT1hweH9ny8z2dHmkIjV7vjUCaDYfVoPag2dtNT6PXwOo yzAQ== X-Gm-Message-State: AOJu0YyNai20Xzv4HNLf2hXzr/IhfdtOsHVwgyGxvAgHHjUKLo7aN0Di WO9ByBaeUfQpfB5UnK/lsSZNaumenOT6unmnA4v+ug0EoihtEGeejBdJTGDzHUiYlzEwhrPxbNM dT1fuOKEn2lsc2Xkqykf74Fvnr0f7R5YL3uVMV8SMeyd0Abkv/YjFngk9fTtpsrx1H+Ajm03+HU O6/o5VWg0Pi5Q0xcNzQmcX8MPiVpKP8NTjAicoZg== X-Gm-Gg: AeBDiesx48/EEo203r/xVn0J5GoP8hDYCa197BeSS5umjMXhOy0YROW148DW9Y67dpp Q6ZIHkaLX3Fwm3aojIrczmC4SIHux7bz8rW3R5l9CVPl7wK7b4h+Fme7B4EiENdUFzTeYMm1qfh cdPrUkWJQy7j3q+5LbHgydYajCVXecb7iglkihn0WD5U1J13QCF97xBZR0pRDmnYU9QuKxfehTk EtOoYyr15CqcKvVVZEXvlU9IQHXtI5S43NhGz466/nqUfQZQYSPVAy4gg/deuTvkPZd4Q+lSi/k /CBbuulgNHlH++aeWN/RnvbRm+AQmbs8G84TltF66wQrodXiqnujPCszTgIh7F/6haV+3ZdsxAt E08EZpZLaGe7SnYNcMqQRqulN2GdQK9Ls+oUM9ZPO/C38 X-Received: by 2002:ac8:6f0d:0:b0:50d:9d34:3b3c with SMTP id d75a77b69052e-50d9d343ca6mr147835321cf.64.1775667366271; Wed, 08 Apr 2026 09:56:06 -0700 (PDT) X-Received: by 2002:ac8:6f0d:0:b0:50d:9d34:3b3c with SMTP id d75a77b69052e-50d9d343ca6mr147834631cf.64.1775667365576; Wed, 08 Apr 2026 09:56:05 -0700 (PDT) From: Peter Xu To: qemu-devel@nongnu.org Cc: "Maciej S . Szmigiero" , =?UTF-8?q?Daniel=20P=20=2E=20Berrang=C3=A9?= , Zhiyi Guo , Juraj Marcin , Peter Xu , Prasad Pandit , Avihai Horon , Kirti Wankhede , =?UTF-8?q?C=C3=A9dric=20Le=20Goater?= , Fabiano Rosas , Joao Martins , Markus Armbruster , Alex Williamson Subject: [PATCH 03/14] vfio/migration: Cache stop size in VFIOMigration Date: Wed, 8 Apr 2026 12:55:47 -0400 Message-ID: <20260408165559.157108-4-peterx@redhat.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260408165559.157108-1-peterx@redhat.com> References: <20260408165559.157108-1-peterx@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=170.10.129.124; envelope-from=peterx@redhat.com; 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, 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_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_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: qemu development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @redhat.com) X-ZM-MESSAGEID: 1775677158366158500 Content-Type: text/plain; charset="utf-8" Add a field to cache stop size. Note that there's an initial value change in vfio_save_setup for the stop size default, but it shouldn't matter if it is followed with a math of MIN() against VFIO_MIG_DEFAULT_DATA_BUFFER_SIZE. Document that all the three sizes we read from VFIO's uAPI on dirty or stop sizes are estimates, so QEMU needs to always remember they can be anything. Signed-off-by: Peter Xu --- hw/vfio/vfio-migration-internal.h | 8 +++++ hw/vfio/migration.c | 50 ++++++++++++++++++------------- 2 files changed, 38 insertions(+), 20 deletions(-) diff --git a/hw/vfio/vfio-migration-internal.h b/hw/vfio/vfio-migration-int= ernal.h index 814fbd9eba..a15fc74703 100644 --- a/hw/vfio/vfio-migration-internal.h +++ b/hw/vfio/vfio-migration-internal.h @@ -45,8 +45,16 @@ typedef struct VFIOMigration { void *data_buffer; size_t data_buffer_size; uint64_t mig_flags; + /* + * NOTE: all three sizes cached are reported from VFIO's uAPI, which + * are defined as estimate only. QEMU should not trust these values + * but only use them to do best-effort estimates. Always be prepared + * that these sizes may either grow or even shrink in reality while + * read()ing from the VFIO fds. + */ uint64_t precopy_init_size; uint64_t precopy_dirty_size; + uint64_t stopcopy_size; bool multifd_transfer; VFIOMultifd *multifd; bool initial_data_sent; diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c index 83327b6573..5d5fca09bd 100644 --- a/hw/vfio/migration.c +++ b/hw/vfio/migration.c @@ -41,6 +41,12 @@ */ #define VFIO_MIG_DEFAULT_DATA_BUFFER_SIZE (1 * MiB) =20 +/* + * Migration size of VFIO devices can be as little as a few KBs or as big = as + * many GBs. This value should be big enough to cover the worst case. + */ +#define VFIO_MIG_STOP_COPY_SIZE (100 * GiB) + static unsigned long bytes_transferred; =20 static const char *mig_state_to_str(enum vfio_device_mig_state state) @@ -314,8 +320,7 @@ static void vfio_migration_cleanup(VFIODevice *vbasedev) migration->data_fd =3D -1; } =20 -static int vfio_query_stop_copy_size(VFIODevice *vbasedev, - uint64_t *stop_copy_size) +static int vfio_query_stop_copy_size(VFIODevice *vbasedev) { uint64_t buf[DIV_ROUND_UP(sizeof(struct vfio_device_feature) + sizeof(struct vfio_device_feature_mig_data_s= ize), @@ -323,16 +328,22 @@ static int vfio_query_stop_copy_size(VFIODevice *vbas= edev, struct vfio_device_feature *feature =3D (struct vfio_device_feature *)= buf; struct vfio_device_feature_mig_data_size *mig_data_size =3D (struct vfio_device_feature_mig_data_size *)feature->data; + VFIOMigration *migration =3D vbasedev->migration; =20 feature->argsz =3D sizeof(buf); feature->flags =3D VFIO_DEVICE_FEATURE_GET | VFIO_DEVICE_FEATURE_MIG_DATA_SIZE; =20 if (ioctl(vbasedev->fd, VFIO_DEVICE_FEATURE, feature)) { + /* + * If getting pending migration size fails, VFIO_MIG_STOP_COPY_SIZE + * is reported so downtime limit won't be violated. + */ + migration->stopcopy_size =3D VFIO_MIG_STOP_COPY_SIZE; return -errno; } =20 - *stop_copy_size =3D mig_data_size->stop_copy_length; + migration->stopcopy_size =3D mig_data_size->stop_copy_length; =20 return 0; } @@ -409,6 +420,16 @@ static void vfio_update_estimated_pending_data(VFIOMig= ration *migration, return; } =20 + /* + * The total size remaining requires separate accounting. Do not trust + * the counter, so what we have read() may be more than what reported. + */ + if (migration->stopcopy_size > data_size) { + migration->stopcopy_size -=3D data_size; + } else { + migration->stopcopy_size =3D 0; + } + if (migration->precopy_init_size) { uint64_t init_size =3D MIN(migration->precopy_init_size, data_size= ); =20 @@ -463,7 +484,6 @@ static int vfio_save_setup(QEMUFile *f, void *opaque, E= rror **errp) { VFIODevice *vbasedev =3D opaque; VFIOMigration *migration =3D vbasedev->migration; - uint64_t stop_copy_size =3D VFIO_MIG_DEFAULT_DATA_BUFFER_SIZE; int ret; =20 if (!vfio_multifd_setup(vbasedev, false, errp)) { @@ -472,9 +492,9 @@ static int vfio_save_setup(QEMUFile *f, void *opaque, E= rror **errp) =20 qemu_put_be64(f, VFIO_MIG_FLAG_DEV_SETUP_STATE); =20 - vfio_query_stop_copy_size(vbasedev, &stop_copy_size); + vfio_query_stop_copy_size(vbasedev); migration->data_buffer_size =3D MIN(VFIO_MIG_DEFAULT_DATA_BUFFER_SIZE, - stop_copy_size); + migration->stopcopy_size); migration->data_buffer =3D g_try_malloc0(migration->data_buffer_size); if (!migration->data_buffer) { error_setg(errp, "%s: Failed to allocate migration data buffer", @@ -570,32 +590,22 @@ static void vfio_state_pending_estimate(void *opaque,= uint64_t *must_precopy, migration->precopy_dirty_size); } =20 -/* - * Migration size of VFIO devices can be as little as a few KBs or as big = as - * many GBs. This value should be big enough to cover the worst case. - */ -#define VFIO_MIG_STOP_COPY_SIZE (100 * GiB) - static void vfio_state_pending_exact(void *opaque, uint64_t *must_precopy, uint64_t *can_postcopy) { VFIODevice *vbasedev =3D opaque; VFIOMigration *migration =3D vbasedev->migration; - uint64_t stop_copy_size =3D VFIO_MIG_STOP_COPY_SIZE; =20 - /* - * If getting pending migration size fails, VFIO_MIG_STOP_COPY_SIZE is - * reported so downtime limit won't be violated. - */ - vfio_query_stop_copy_size(vbasedev, &stop_copy_size); - *must_precopy +=3D stop_copy_size; + vfio_query_stop_copy_size(vbasedev); + *must_precopy +=3D migration->stopcopy_size; =20 if (vfio_device_state_is_precopy(vbasedev)) { vfio_query_precopy_size(migration); } =20 trace_vfio_state_pending_exact(vbasedev->name, *must_precopy, *can_pos= tcopy, - stop_copy_size, migration->precopy_init= _size, + migration->stopcopy_size, + migration->precopy_init_size, migration->precopy_dirty_size); } =20 --=20 2.53.0