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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: Xh0qMf6RT9KDF7i5cjkVZYPJHOZUmi4Ndi/lh9I2WVS/LtnR6au1NC1wefPdoKgUZrJ5/ZrZF8vmOTEjIfDLIxZ9L6W87rxgb5AifEDsOIEJzo3K50khKtRIWla6weoT7Vg+gCtcL83/OBYru8lIw7QmBoBA0/B+zRFlMlBp7tvT1s1GZ//f5rICMODjyIEE52Bn2YEDV3reA+I8ookEkJJaaHPC53NcdSXAN4Y8hJerwl5OL1B9cimv7SYVLYF2K4rZekuPk+ifywx8vBK09Bs3yb8N5+ocUjIXV/nItHOzts90OEH8Oc92pUp1hXD9asT5jlENKcvZX0/7MqaFnsg0+iIec2j5uEydopIY54zffeHxUzp3u9VHGVBd1Dwtgi3LBv0lmtsv0YB/hvtgQwuhn4wInjJqzpEsbyzIE6NT4Afw0EynVQOYW4O6xWba X-ExternalRecipientOutboundConnectors: 0bc7f26d-0264-416e-a6fc-8352af79c58f X-Auto-Response-Suppress: DR, OOF, AutoReply X-OriginatorOrg: virtuozzo.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 09 Oct 2026 15:22:39.6014 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: ae784e21-ce6f-4d4d-0592-08df261927fd X-MS-Exchange-CrossTenant-Id: 0bc7f26d-0264-416e-a6fc-8352af79c58f X-MS-Exchange-CrossTenant-AuthSource: CPH1EPF00000524.eurprd05.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: Internet X-MS-Exchange-Transport-CrossTenantHeadersStamped: PAVPR08MB8799 > kvm_close() destroys the vCPUs, which unmaps their kvm_run areas, and the > coalesced MMIO ring lives in the kvm_run area of the first vCPU. Nothing > stops the RCU thread from flushing that ring at the same time: finalizing > a memory region of a freed flatview calls memory_region_transaction_begin= () > and thus kvm_flush_coalesced_mmio_buffer(). kvm_state is still set at > that point, so the flush reads the ring after it has been unmapped: >=20 > #0 kvm_flush_coalesced_mmio_buffer accel/kvm/kvm-all.c > #1 qemu_flush_coalesced_mmio_buffer > #2 memory_region_transaction_begin > #3 memory_region_finalize > ... > #10 flatview_destroy > #11 call_rcu_thread >=20 > while the main thread is in: >=20 > kvm_close -> cpu_remove_sync > vfio_kvm_device_close > vfio_cpr_kvm_close_notifier (MIG_EVENT_PRECOPY_DONE) >=20 > Seen as a SIGSEGV of the old QEMU during repeated cpr-exec of a VM with > a VFIO device. >=20 > Clear the ring pointer first, so that new flushes skip it, and wait for > the pending RCU callbacks before destroying the vCPUs. >=20 > Fixes: 7ed0919119b0 ("migration: close kvm after cpr") > Signed-off-by: Andrey Drobyshev Sashiko has reviewed this patch and found no issues. It looks great! --=20 Sashiko AI review =C2=B7 https://sashiko.vzint.dev/#/patchset/20261009-vfio= _v1-v1-0-2ae91d5b8048@virtuozzo.com?part=3D15