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

[Juergen Gross]

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.

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.


Juergen

0001-xen-introduce-dummy-system-device.patch
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