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a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1734105686; h=from:from:reply-to: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=RwiVLOerfW9Cfdhb0cJ1TgrGYEBCJdwy+qViOmssyjE=; b=ZfnKYQCbnW2y0iAgiNvGg4lkJ1Z4+8tj1uJ2VA0gFnwur+0Ml6zRzxk7ZZ6U+reou5S/19 nEAbV6Sf29pqiKAw== From: Fabiano Rosas To: qemu-devel@nongnu.org Cc: Peter Xu , qemu-stable@nongnu.org Subject: [PATCH 1/2] migration/multifd: Fix compat with QEMU < 9.0 Date: Fri, 13 Dec 2024 13:01:19 -0300 Message-Id: <20241213160120.23880-2-farosas@suse.de> X-Mailer: git-send-email 2.35.3 In-Reply-To: <20241213160120.23880-1-farosas@suse.de> References: <20241213160120.23880-1-farosas@suse.de> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 41B8A1F78D X-Spam-Score: -3.01 X-Rspamd-Action: no action X-Spamd-Result: default: False [-3.01 / 50.00]; BAYES_HAM(-3.00)[99.99%]; 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envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=2a07:de40:b251:101:10:150:64:2; envelope-from=farosas@suse.de; helo=smtp-out2.suse.de X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, SPF_HELO_NONE=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+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @suse.de) X-ZM-MESSAGEID: 1734105730797116600 Content-Type: text/plain; charset="utf-8" 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 Signed-off-by: Fabiano Rosas Reviewed-by: Peter Xu --- migration/multifd.c | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-) 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 2.35.3