Re: [PATCH v11 01/17] libxl: fix stubdom console destruction

[Roger Pau Monne <roger.pau@citrix.com>]

Ian Campbell wrote:
> On Mon, 2012-07-23 at 18:27 +0100, Roger Pau Monne wrote:
>> Stubdoms have several consoles attached, and they don't follow the
>> xenstore protocol for devices, since they are always in state 1. We
>> have to add an exception to libxl__initiate_device_remove, so libxl
>> doesn't wait for them to reach state 6 (Closed).
>>
>> Report: http://markmail.org/message/yqgppcsdip6tnmh6
>>
>> Cc: Ian Jackson <ian.jackson@eu.citrix.com>
>> Reported-by: Ian Campbell <ian.campbell@eu.citrix.com>
>> Signed-off-by: Roger Pau Monne <roger.pau@citrix.com>
>> ---
>>  tools/libxl/libxl_device.c |    6 ++++--
>>  1 files changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/tools/libxl/libxl_device.c b/tools/libxl/libxl_device.c
>> index a94beab..c4392fa 100644
>> --- a/tools/libxl/libxl_device.c
>> +++ b/tools/libxl/libxl_device.c
>> @@ -592,8 +592,10 @@ void libxl__initiate_device_remove(libxl__egc *egc,
>>          LOG(ERROR, "unable to get info for domain %d", domid);
>>          goto out;
>>      }
>> -    if (QEMU_BACKEND(aodev->dev) &&
>> -        (info.paused || info.dying || info.shutdown)) {
>> +    if ((QEMU_BACKEND(aodev->dev) &&
>> +        (info.paused || info.dying || info.shutdown)) ||
>> +        (libxl_is_stubdom(CTX, aodev->dev->domid, NULL) &&
>> +        (aodev->dev->backend_kind == LIBXL__DEVICE_KIND_CONSOLE))) {
> 
> Is this actually specific to stubdom consoles or is that just where
> we've noticed it?

It's just that I've noticed it with stubdoms, which AFAIK are the only
domains that can have more than one console.

> I don't see why it wouldn't be relevant to any PV
> console other than the first (which I assume you special case
> elsewhere?)

Yes, the PV console special case was already there before my changes, I
just left it untouched.

> Probably the logic would be clearer in a helper, i.e.
> dev_is_stubdom_console? or encapsulate both bits of logic in
> dev_needs_shutdown?

Yes.

> Does it apply to LIBXL__CONSOLE_BACKEND_IOEMU as well
> as ..._XENCONSOLED? I took a look through tools/console and I cannot
> find any handling of a state node in xenstore at all, so the XENCONSOLED
> case seems clear. I notice that xen_console.c registers the device with
> DEVOPS_FLAG_IGNORE_STATE but that only seems to affect startup not
> teardown. I don't see a qemu_chr_close (or anything similar) anywhere in
> hw/xen_console.c

So it should apply to any console device? This means I don't have to
wait for any device of type LIBXL__DEVICE_KIND_CONSOLE, and there's no
need to check for the specific console type or Qemu.

> 
>>          /*
>>           * TODO: 4.2 Bodge due to QEMU, see comment on top of
>>           * libxl__initiate_device_remove in libxl_internal.h
> 
> I suppose this comment needs updating now that the conditional has
> changed? In particular the special handling of consoles is not a qemu
> related bodge.

I thought it was a Qemu related issue, but I will change the comment or
do this check in a different "if".