Re: [Qemu-block] [PATCH] block/file-posix: add bdrv_attach_aio_context callback for host dev and cdrom

[Farhan Ali]

On 07/23/2018 12:30 PM, Stefan Hajnoczi wrote:
> On Fri, Jul 20, 2018 at 03:11:14PM -0400, Farhan Ali wrote:
> > I am seeing another issue pop up, in a different test. Even though it's a
> > different assertion, it might be related based on the call trace.
>
> Which test case?

This test case involved one guest with 2 disks, with an iothread for 
each disk. The guest was running a memory workload.

> > Stack trace of thread 276199:
> > #0  0x000003ff8473e274 raise (libc.so.6)
> > #1  0x000003ff847239a8 abort (libc.so.6)
> > #2  0x000003ff847362ce __assert_fail_base (libc.so.6)
> > #3  0x000003ff8473634c __assert_fail (libc.so.6)
> > #4  0x000002aa30aba0c4 iov_memset (qemu-system-s390x)
> > #5  0x000002aa30aba9a6 qemu_iovec_memset (qemu-system-s390x)
> > #6  0x000002aa30a23e88 qemu_laio_process_completion (qemu-system-s390x)
>
> What are the values of laiocb->qiov->size and laiocb->ret?

The laiocb->qiov->size was 4096 and laiocb->ret was 8192

> > #7  0x000002aa30a23f68 qemu_laio_process_completions (qemu-system-s390x)
> > #8  0x000002aa30a2418e qemu_laio_process_completions_and_submit
> > (qemu-system-s390x)
> > #9  0x000002aa30a24220 qemu_laio_poll_cb (qemu-system-s390x)
> > #10 0x000002aa30ab22c4 run_poll_handlers_once (qemu-system-s390x)
> > #11 0x000002aa30ab2e78 aio_poll (qemu-system-s390x)
> > #12 0x000002aa30a29f4e bdrv_do_drained_begin (qemu-system-s390x)
> > #13 0x000002aa30a2a276 bdrv_drain (qemu-system-s390x)
> > #14 0x000002aa309d45aa bdrv_set_aio_context (qemu-system-s390x)
> > #15 0x000002aa3085acfe virtio_blk_data_plane_stop (qemu-system-s390x)
> > #16 0x000002aa3096994c virtio_bus_stop_ioeventfd.part.1 (qemu-system-s390x)
> > #17 0x000002aa3087d1d6 virtio_vmstate_change (qemu-system-s390x)
> > #18 0x000002aa308e8a12 vm_state_notify (qemu-system-s390x)
> > #19 0x000002aa3080ed54 do_vm_stop (qemu-system-s390x)
> > #20 0x000002aa307bea04 main (qemu-system-s390x)
> > #21 0x000003ff84723dd2 __libc_start_main (libc.so.6)
> > #22 0x000002aa307c0414 _start (qemu-system-s390x)
> >
> >
> > The failing assertion is:
> >
> > qemu-kvm: util/iov.c:78: iov_memset: Assertion `offset == 0' failed.
>
> I wonder if the offset is beyond the end of the iovecs.
>
> Thanks,
> Stefan

Thanks
Farhan