Am 03.05.2018 um 14:17 hat Markus Armbruster geschrieben:
> Kevin Wolf <kw...@redhat.com> writes:
>
> > Am 23.04.2018 um 10:45 hat Markus Armbruster geschrieben:
> >> When resume of a stopped guest immediately runs into block device
> >> errors, the BLOCK_IO_ERROR event is sent before the RESUME event.
> >>
> >> Reproducer:
> >>
> >> 1. Create a scratch image
> >> $ dd if=/dev/zero of=scratch.img bs=1M count=100
> >>
> >> Size doesn't actually matter.
> >>
> >> 2. Prepare blkdebug configuration:
> >>
> >> $ cat >blkdebug.conf <<EOF
> >> [inject-error]
> >> event = "write_aio"
> >> errno = "5"
> >> EOF
> >>
> >> Note that errno 5 is EIO.
> >>
> >> 3. Run a guest with an additional scratch disk, i.e. with additional
> >> arguments
> >> -drive
> >> if=none,id=scratch-drive,format=raw,werror=stop,file=blkdebug:blkdebug.conf:scratch.img
> >> -device virtio-blk-pci,id=scratch,drive=scratch-drive
> >>
> >> The blkdebug part makes all writes to the scratch drive fail with
> >> EIO. The werror=stop pauses the guest on write errors.
> >>
> >> 4. Connect to the QMP socket e.g. like this:
> >> $ socat UNIX:/your/qmp/socket
> >> READLINE,history=$HOME/.qmp_history,prompt='QMP> '
> >>
> >> Issue QMP command 'qmp_capabilities':
> >> QMP> { "execute": "qmp_capabilities" }
> >>
> >> 5. Boot the guest.
> >>
> >> 6. In the guest, write to the scratch disk, e.g. like this:
> >>
> >> # dd if=/dev/zero of=/dev/vdb count=1
> >>
> >> Do double-check the device specified with of= is actually the
> >> scratch device!
> >>
> >> 7. Issue QMP command 'cont':
> >> QMP> { "execute": "cont" }
> >>
> >> After step 6, I get a BLOCK_IO_ERROR event followed by a STOP event. Good.
> >>
> >> After step 7, I get BLOCK_IO_ERROR, then RESUME, then STOP. Not so
> >> good; I'd expect RESUME, then BLOCK_IO_ERROR, then STOP.
> >
> > Do you want to rephrase this in the form of a script for qemu-iotests?
> >
> > I suppose the 'dd' line can be replaced by a 'qemu-io' monitor command.
>
> Uh, can it? With qemu-io, the write doesn't stop the guest, because it
> bypasses the device model, and thus blk_error_action(). I'm not aware
> of ways to make qemu-iotests write via a device model. I'm afraid we
> need a full-fledged qtest. Better ideas?
I'm afraid you're right. :-(
Did I ever mention that I don't really like having the werror logic in
the devices?
Kevin
