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

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Mon, Mar 07, 2016 at 08:21:46AM +0100, Juergen Gross wrote:
> 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.
> 

Yes. I need this device. I'm not sure what "hiding this device in
backend" means though.

Wei.

> Juergen

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