Re: Regression save/restore of vsock: (was [PULL 07/55] hw/virtio: move vm_running check to virtio_device_started)

["Alex Bennée" <alex.bennee@linaro.org>]

Christian Borntraeger <borntraeger@linux.ibm.com> writes:

> Am 10.10.22 um 19:29 schrieb Michael S. Tsirkin:
>> From: Alex Bennée <alex.bennee@linaro.org>
>> All the boilerplate virtio code does the same thing (or should at
>> least) of checking to see if the VM is running before attempting to
>> start VirtIO. Push the logic up to the common function to avoid
>> getting a copy and paste wrong.
>> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
>> Message-Id: <20220802095010.3330793-11-alex.bennee@linaro.org>
>> Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
>> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
>
> This results in a regression for our s390x CI when doing save/restore of guests with vsock:
>
>
>                 #1  0x000003ff9a248580 raise (libc.so.6 + 0x48580)
>                 #2  0x000003ff9a22b5c0 abort (libc.so.6 + 0x2b5c0)
>                 #3  0x000003ff9a2409da __assert_fail_base (libc.so.6 + 0x409da)
>                 #4  0x000003ff9a240a4e __assert_fail (libc.so.6 + 0x40a4e)
>                 #5  0x000002aa2d69a066 vhost_vsock_common_pre_save (qemu-system-s390x + 0x39a066)
>                 #6  0x000002aa2d55570e vmstate_save_state_v (qemu-system-s390x + 0x25570e)
>                 #7  0x000002aa2d556218 vmstate_save_state (qemu-system-s390x + 0x256218)
>                 #8 0x000002aa2d570ba4
> qemu_savevm_state_complete_precopy_non_iterable (qemu-system-s390x +
> 0x270ba4)
>                 #9  0x000002aa2d5710b6 qemu_savevm_state_complete_precopy (qemu-system-s390x + 0x2710b6)
>                 #10 0x000002aa2d564d0e migration_completion (qemu-system-s390x + 0x264d0e)
>                 #11 0x000002aa2d8db25c qemu_thread_start (qemu-system-s390x + 0x5db25c)
>                 #12 0x000003ff9a296248 start_thread (libc.so.6 + 0x96248)
>                 #13 0x000003ff9a31183e thread_start (libc.so.6 + 0x11183e)

Which test does this break?

Looking at the change the only thing I can think of is there is a subtle
change in the order of checks because if the device is set as
use_started we return the result regardless of vm or config state:

    if (vdev->use_started) {
        return vdev->started;
    }

Could some printfs confirm that?

-- 
Alex Bennée