From mboxrd@z Thu Jan  1 00:00:00 1970
From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Subject: Re: [PATCH 08/13] Xen paravirtualised PCI hotplug.
Date: Mon, 19 Oct 2009 10:50:36 -0400
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Cc: Jeremy Fitzhardinge <jeremy@goop.org>, "xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>, Yosuke Iwamatsu <y-iwamatsu@ab.jp.nec.com>
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>> +	XenbusStateReconfiguring = 7,
>> +
>> +	XenbusStateReconfigured  = 8
>>  };
>>   
> ouch.
>
> what's the usefulness of those 2 new states here ?

The changes came originally from the c/s 17223, which was titled:
Add PV passthrough PCI device hotplug support.

The short summary of that is that you can dynamically attach
PCI devices by doing: 'xm pci-attach'. And also detach by doing 'xm pci-dettach'.

> the xenbus state is just here to represent the connection status of the  
> xenbus device, doesn't reconfiguring/reconfigured state is something  
> about the underlying device more than the xenbus device ?

I suppose it is. Thought it is more of a state of evolution - the blkback
device could support changing of size dynamically (for example if it was mounted
on raw LUN which changed size as well). Or if the blkback was binded to a CD-ROM
device - support reconfiguring it (new media perhaps?).

>
> And regarding the xenbus-state state machine, what happen when you reach 8 ?
> does every userspace handler need to handle it as a 4 ? if yes why is it  
> not 4 ?

Good question. Lets ask Yosuke Iwamatsu who posted the initial
patch for this.