From nobody Sat Apr 5 15:38:47 2025 Delivered-To: importer@patchew.org Authentication-Results: mx.zohomail.com; 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 Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 173798800734043.501180920438856; Mon, 27 Jan 2025 06:26:47 -0800 (PST) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1tcQ1K-00081b-Ur; Mon, 27 Jan 2025 09:23:23 -0500 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 1tcQ1G-0007kV-Vo; Mon, 27 Jan 2025 09:23:19 -0500 Received: from isrv.corpit.ru ([86.62.121.231]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1tcQ1F-0002uf-7G; Mon, 27 Jan 2025 09:23:18 -0500 Received: from localhost.tls.msk.ru (mjt.wg.tls.msk.ru [192.168.177.130]) by isrv.corpit.ru (Postfix) with ESMTP id E6D3BE0F53; Mon, 27 Jan 2025 17:22:47 +0300 (MSK) Received: by localhost.tls.msk.ru (Postfix, from userid 1000) id 8338D51D87; Mon, 27 Jan 2025 17:18:03 +0300 (MSK) From: Michael Tokarev To: qemu-devel@nongnu.org Cc: qemu-stable@nongnu.org, Fabiano Rosas , Peter Xu , Michael Tokarev Subject: [Stable-9.2.1 17/41] migration/multifd: Fix compat with QEMU < 9.0 Date: Mon, 27 Jan 2025 17:17:31 +0300 Message-Id: <20250127141803.3514882-17-mjt@tls.msk.ru> X-Mailer: git-send-email 2.39.5 In-Reply-To: References: 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=86.62.121.231; envelope-from=mjt@tls.msk.ru; helo=isrv.corpit.ru X-Spam_score_int: -68 X-Spam_score: -6.9 X-Spam_bar: ------ X-Spam_report: (-6.9 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_DNSWL_HI=-5, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, 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+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZM-MESSAGEID: 1737988008749019000 Content-Type: text/plain; charset="utf-8" From: Fabiano Rosas Commit f5f48a7891 ("migration/multifd: Separate SYNC request with normal jobs") changed the multifd source side to stop sending data along with the MULTIFD_FLAG_SYNC, effectively introducing the concept of a SYNC-only packet. Relying on that, commit d7e58f412c ("migration/multifd: Don't send ram data during SYNC") later came along and skipped reading data from SYNC packets. In a versions timeline like this: 8.2 f5f48a7 9.0 9.1 d7e58f41 9.2 The issue arises that QEMUs < 9.0 still send data along with SYNC, but QEMUs > 9.1 don't gather that data anymore. This leads to various kinds of migration failures due to desync/missing data. Stop checking for a SYNC packet on the destination and unconditionally unfill the packet. >From now on: old -> new: the source sends data + sync, destination reads normally new -> new: source sends only sync, destination reads zeros new -> old: source sends only sync, destination reads zeros CC: qemu-stable@nongnu.org Fixes: d7e58f412c ("migration/multifd: Don't send ram data during SYNC") Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2720 Reviewed-by: Peter Xu Signed-off-by: Fabiano Rosas Message-Id: <20241213160120.23880-2-farosas@suse.de> Signed-off-by: Fabiano Rosas (cherry picked from commit b93d897ea2f0abbe7fc341a9ac176b5ecd0f3c93) Signed-off-by: Michael Tokarev diff --git a/migration/multifd.c b/migration/multifd.c index 498e71fd10..8d0a763a72 100644 --- a/migration/multifd.c +++ b/migration/multifd.c @@ -252,9 +252,8 @@ static int multifd_recv_unfill_packet(MultiFDRecvParams= *p, Error **errp) p->packet_num =3D be64_to_cpu(packet->packet_num); p->packets_recved++; =20 - if (!(p->flags & MULTIFD_FLAG_SYNC)) { - ret =3D multifd_ram_unfill_packet(p, errp); - } + /* Always unfill, old QEMUs (<9.0) send data along with SYNC */ + ret =3D multifd_ram_unfill_packet(p, errp); =20 trace_multifd_recv_unfill(p->id, p->packet_num, p->flags, p->next_packet_size); @@ -1151,9 +1150,13 @@ static void *multifd_recv_thread(void *opaque) flags =3D p->flags; /* recv methods don't know how to handle the SYNC flag */ p->flags &=3D ~MULTIFD_FLAG_SYNC; - if (!(flags & MULTIFD_FLAG_SYNC)) { - has_data =3D p->normal_num || p->zero_num; - } + + /* + * Even if it's a SYNC packet, this needs to be set + * because older QEMUs (<9.0) still send data along with + * the SYNC packet. + */ + has_data =3D p->normal_num || p->zero_num; qemu_mutex_unlock(&p->mutex); } else { /* --=20 2.39.5