Tunnelled migration can hang if the destination qemu exits despite all the ABI checks. This happens whenever the destination qemu exits before the complete transfer. The savevm state checks at runtime can fail at destination qemu and error out. The source qemu cant notice it as the EPIPE is not propogated to qemu. The qemuMigrationIOFunc() notices the stream being broken from virStreamSend() and it cleans up the stream alone. The qemuMigrationWaitForCompletion() would never get to 100% transfer completion. The qemuMigrationWaitForCompletion() never breaks out as well since the ssh connection to destination is healthy, and the source qemu also thinks the migration is ongoing as the Fd to which it transfers, is never closed or broken. So, the migration will hang forever. Even Ctrl-C on the virsh migrate wouldn't be honoured. Close the source side FD when there is an error in the stream. That way, the source qemu updates itself and qemuMigrationWaitForCompletion() notices the failure. Close the FD for all kinds of errors to be sure. The error message is not copied for EPIPE so that the destination error is copied instead later. Note: Reproducible with repeated migrations between Power hosts running in different subcores-per-core modes. Signed-off-by: Shivaprasad G Bhat <sbhat(a)linux.vnet.ibm.com&gt; --- src/qemu/qemu_migration.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/src/qemu/qemu_migration.c b/src/qemu/qemu_migration.c index ff89ab5..4f9aced 100644 --- a/src/qemu/qemu_migration.c +++ b/src/qemu/qemu_migration.c @@ -4029,7 +4029,11 @@ static void qemuMigrationIOFunc(void *arg) } error: - virCopyLastError(&data->err); + /* Let the source qemu know that the transfer can't continue anymore. + * Don't copy the error for EPIPE as destination has the actual error */ + VIR_FORCE_CLOSE(data->sock); + if (!virLastErrorIsSystemErrno(EPIPE)) + virCopyLastError(&data->err); virResetLastError(); VIR_FREE(buffer); }