When is "physical-device" created in xenstore?

When is "physical-device" created in xenstore?

[Tian, Kevin]

Saw a strange problem. When blkfront writes event channel number and
ring-ref to xenstore, the watch registered by blkback is notified.
However immediately watch handler in blkback found there's no
"physical-device" under xenstore which should refer to major/minor
number of device for domU. Then failed to create vbd and finally the
connection can't be setup.

So my puzzle is, when should physical-device be created? And who creates
this item? I searched for name string in whole tools directory to only
find instance in block-file/block-phy/block-endb. I configured disk
image by /dev/loop0, so ideally block-phy should be used. However I
still failed to find where block-phy is invoked.

Any clues?

Thanks,
Kevin

RE: When is "physical-device" created in xenstore?

[Tian, Kevin]

If making following temp hack in XendDomainInfo.py:

             back = { 'type' : type,
                      'params' : params,
                      'frontend' : frontpath,
-                     'frontend-id' : "%i" % self.domid }
+                     'frontend-id' : "%i" % self.domid,
+                    'physical-device' : "%li" % blkdev_name_to_number(params) }
             xstransact.Write(backpath, back)

Then physical-device is created under backend and the communication can be setup. However this hard code definitely breaks existing logical behind. Should I do any specific configuration? From the Blkctl.py, it said that "phy" type doesn't require bind/unbind script, but I didn't find the place to add that item specifically. ;-(

Thanks,
Kevin

>-----Original Message-----
>From: xen-devel-bounces@lists.xensource.com
>[mailto:xen-devel-bounces@lists.xensource.com] On Behalf Of Tian, Kevin
>Sent: 2005年9月20日 16:37
>To: xen-devel@lists.xensource.com
>Subject: [Xen-devel] When is "physical-device" created in xenstore?
>
>Saw a strange problem. When blkfront writes event channel number and
>ring-ref to xenstore, the watch registered by blkback is notified.
>However immediately watch handler in blkback found there's no
>"physical-device" under xenstore which should refer to major/minor
>number of device for domU. Then failed to create vbd and finally the
>connection can't be setup.
>
>So my puzzle is, when should physical-device be created? And who creates
>this item? I searched for name string in whole tools directory to only
>find instance in block-file/block-phy/block-endb. I configured disk
>image by /dev/loop0, so ideally block-phy should be used. However I
>still failed to find where block-phy is invoked.
>
>Any clues?
>
>Thanks,
>Kevin
>
>_______________________________________________
>Xen-devel mailing list
>Xen-devel@lists.xensource.com
>http://lists.xensource.com/xen-devel

Re: When is "physical-device" created in xenstore?

[Ewan Mellor]

On Tue, Sep 20, 2005 at 07:41:09PM +0800, Tian, Kevin wrote:

> If making following temp hack in XendDomainInfo.py:
> 
>              back = { 'type' : type,
>                       'params' : params,
>                       'frontend' : frontpath,
> -                     'frontend-id' : "%i" % self.domid }
> +                     'frontend-id' : "%i" % self.domid,
> +                    'physical-device' : "%li" % blkdev_name_to_number(params) }
>              xstransact.Write(backpath, back)
> 
> Then physical-device is created under backend and the communication can be
> setup. However this hard code definitely breaks existing logical
> behind. Should I do any specific configuration? From the Blkctl.py, it said
> that "phy" type doesn't require bind/unbind script, but I didn't find the
> place to add that item specifically. ;-(

Hi Kevin,

The key physical-device is created inside the block-phy script, as I think you
found.  This is called by xen-backend.agent, which in turn is called by the
Linux hotplug system (keying off the name 'xen-backend').  The file Blkctl.py
is completely unused, AFAICT, and should be removed.

The problems that you are having starting your device are probably down to a
broken or nonexistent installation of the hotplug system.  You should check
that first.  If your hotplug system is working, then maybe you are failing to
find xenstore-write.

HTH,

Ewan.

RE: When is "physical-device" created in xenstore?

[Tian, Kevin]

>From: Ewan Mellor [mailto:ewan@xensource.com]
>Sent: 2005年9月20日 21:12
>On Tue, Sep 20, 2005 at 07:41:09PM +0800, Tian, Kevin wrote:
>
>> If making following temp hack in XendDomainInfo.py:
>>
>>              back = { 'type' : type,
>>                       'params' : params,
>>                       'frontend' : frontpath,
>> -                     'frontend-id' : "%i" % self.domid }
>> +                     'frontend-id' : "%i" % self.domid,
>> +                    'physical-device' : "%li" %
>blkdev_name_to_number(params) }
>>              xstransact.Write(backpath, back)
>>
>> Then physical-device is created under backend and the communication can be
>> setup. However this hard code definitely breaks existing logical
>> behind. Should I do any specific configuration? From the Blkctl.py, it said
>> that "phy" type doesn't require bind/unbind script, but I didn't find the
>> place to add that item specifically. ;-(
>
>Hi Kevin,
>
>The key physical-device is created inside the block-phy script, as I think you
>found.  This is called by xen-backend.agent, which in turn is called by the
>Linux hotplug system (keying off the name 'xen-backend').  The file Blkctl.py
>is completely unused, AFAICT, and should be removed.
>
>The problems that you are having starting your device are probably down to a
>broken or nonexistent installation of the hotplug system.  You should check
>that first.  If your hotplug system is working, then maybe you are failing to
>find xenstore-write.
>
>HTH,
>
>Ewan.

Hi, Ewan,
	Thanks for your description about the work flow. Actually I found the cause from bad lines in xen-backend.script, which has already been fixed by Keir several days ago. After removing the bad lines, the "physical-device" can be created automatically.

Thanks,
Kevin