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Re: [libvirt] [PATCH 0/2] qemu: Rework CD/DVD changing



On 17.05.2013 10:16, Li Wei wrote:
> On 05/17/2013 04:07 PM, Michal Privoznik wrote:
>> On 17.05.2013 07:47, Li Wei wrote:
>>> Hi Michal, Daniel
>>>
>>> It seems there is something wrong with the 2/2 part of this patchset.
>>> When I do an "change-media" command in virsh, it doesn't do any better
>>> than before, but even worse(I must to wait 5 secs to see the error).
>>>
>>> I'm not family with libvirt, just add some log things in the qemu_hotplug.c
>>> and found the tray_status never change to open, but with michal's original
>>> patch (which do active poll on tray_status), I can do "change-media" successfully
>>> every time.
>>
>> Yes & no. Thing is - originally we ignored tray status in the guest. So
>> in case guest has locked the tray and thus ignored our eject request, we
>> have changed the media anyway, resulting in possible I/O errors within
>> guest.
>>
>> With my patch, we send eject request to the qemu, and actively poll for
>> the tray to open. We check for up to 10 times every 200ms. So guest has
>> 2 seconds to open the tray. If the guest doesn't eject media and open
>> the tray we don't proceed with forcibly changing the media.
>>
>> These patches are actually a bug fix for
>> https://bugzilla.redhat.com/show_bug.cgi?id=892289
> 
> Hmm... I think you misunderstood my meaning(sorry for my pool english),
> simply to say, I can get expected behavior by apply patch V1 but not V2.
> 
> In V1, we do active poll on qemuMonitorGetBlockInfo(), and in V2 we just
> wait for origdisk->tray_status to become VIR_DOMAIN_DISK_TRAY_OPEN but
> this never happened.
> 
> Thanks,
> Wei

Aaah, now I understand. So you are saying that the event is not being
delivered. What's the qemu version?

If you turn the debug logs on, do you see DEVICE_TRAY_MOVED in them?
http://wiki.libvirt.org/page/DebugLogs

Or maybe the timeout is just short for your guest to eject the tray. So
after a while, does 'virsh change-media' succeed?

Michal

> 
>>
>>>
>>> IMHO, there must be some bug in the processing of qemu tray change.
>>>
>>> Thanks,
>>> Wei
>>>
>>>
>>> On 01/25/2013 08:20 PM, Michal Privoznik wrote:
>>>> The first patch is bare bug fix (without any bug reported though).
>>>> The second is again a bug fix, but not so easy to spot. Basically, when we
>>>> change a media, we should issue 'eject' first, then wait until the tray gets
>>>> open, after which we can finally issue 'change' command. Even for bare 'eject'
>>>> we ought to check status, shouldn't we?
>>>>
>>>> Michal Privoznik (2):
>>>>   qemu_monitor: Fix tray-open attribute in query-block
>>>>   qemu_hotplug: Rework media changing process
>>>>
>>>>  src/qemu/qemu_hotplug.c      | 51 +++++++++++++++++++++++++++++++++++++++++---
>>>>  src/qemu/qemu_monitor_json.c |  2 +-
>>>>  src/qemu/qemu_monitor_text.c |  6 +++---
>>>>  3 files changed, 52 insertions(+), 7 deletions(-)
>>>>
>>
>>
> 
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