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| author | Fabiano Rosas <farosas@suse.de> | 2024-12-13 13:01:19 -0300 |
|---|---|---|
| committer | Fabiano Rosas <farosas@suse.de> | 2025-01-09 17:38:35 -0300 |
| commit | b93d897ea2f0abbe7fc341a9ac176b5ecd0f3c93 (patch) | |
| tree | 6cd2f881ac9bc165b29d93bbfec23d847a2beca3 | |
| parent | baab4473dba2b85adf3c0622b92bc209f7a8dec0 (diff) | |
| download | qemu-b93d897ea2f0abbe7fc341a9ac176b5ecd0f3c93.zip qemu-b93d897ea2f0abbe7fc341a9ac176b5ecd0f3c93.tar.gz qemu-b93d897ea2f0abbe7fc341a9ac176b5ecd0f3c93.tar.bz2 | |
migration/multifd: Fix compat with QEMU < 9.0
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 <peterx@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Message-Id: <20241213160120.23880-2-farosas@suse.de>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
| -rw-r--r-- | migration/multifd.c | 15 |
1 files changed, 9 insertions, 6 deletions
diff --git a/migration/multifd.c b/migration/multifd.c index 64e0ac2..ab73d6d 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 = be64_to_cpu(packet->packet_num); p->packets_recved++; - if (!(p->flags & MULTIFD_FLAG_SYNC)) { - ret = multifd_ram_unfill_packet(p, errp); - } + /* Always unfill, old QEMUs (<9.0) send data along with SYNC */ + ret = multifd_ram_unfill_packet(p, errp); trace_multifd_recv_unfill(p->id, p->packet_num, p->flags, p->next_packet_size); @@ -1156,9 +1155,13 @@ static void *multifd_recv_thread(void *opaque) flags = p->flags; /* recv methods don't know how to handle the SYNC flag */ p->flags &= ~MULTIFD_FLAG_SYNC; - if (!(flags & MULTIFD_FLAG_SYNC)) { - has_data = 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 = p->normal_num || p->zero_num; qemu_mutex_unlock(&p->mutex); } else { /* |