Re: [Xen-devel] [Qemu-devel] RFC: configuring QEMU virtfs for Xen PV(H) guests

[Juergen Gross <jgross@xxxxxxxx>]

Hi Wei,

On 15/02/16 14:44, Wei Liu wrote:
> On Mon, Feb 15, 2016 at 02:33:05PM +0100, Juergen Gross wrote:
>> On 15/02/16 14:16, Wei Liu wrote:
>>> On Mon, Feb 15, 2016 at 09:07:13AM +0000, Paul Durrant wrote:
>>>>>
>>> [...]
>>>>> # Option 2: Invent a xen-9p device
>>>>>
>>>>> Another way of doing it is to expose a dummy xen-9p device, so that we
>>>>> can use -fsdev XXX -device xen-9p,YYY.  This simple device should be
>>>>> used to capture the parameters like mount_tag and fsdev_id, and then
>>>>> chained itself to a known location.  Later Xen transport can traverse
>>>>> this known location. This xen-9p device doesn't seem to fit well into
>>>>> the hierarchy. The best I can think of its parent should be
>>>>> TYPE_DEVICE.  In this case:
>>>>>
>>>>> 1. Toolstack arranges some xenstore entries.
>>>>> 2. Toolstack arranges command line options for QEMU:
>>>>>       -fsdev XXX -device xen-9p,XXX
>>>>> 3. QEMU starts up in xen-attach mode, scans xenstore for relevant
>>>>>    entries, then traverses the known location.
>>>>>
>>>>> Downside: Inventing a dummy device looks suboptimal to me.
>>
>> Sorry, didn't notice this thread before.
>>
> 
> No need to be sorry. I posted this last Friday night. I wouldn't expect
> many replies on Monady.
> 
>> For Xen pvUSB backend in qemu I need a Xen system device acting as
>> parent for being able to attach/detach virtual USB busses.
>>
>> I haven't had time to update my patches for some time, but the patch
>> for this system device is rather easy. It could be used as a parent
>> of the xen-9p devices, too.
>>
>> I've attached the patch for reference.
>>
> 
> Thanks. I will have a look at your patch.

Did you have some time to look at the patch? I'm asking because I
finally found some time to start working on V2 of my qemu based pvUSB
backend. Stefano asked me to hide the system device in my backend and
I want to avoid that in case you are needing it, too.

Juergen

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