Re: [Qemu-devel] [Xen-devel] [PATCH] Citrix PV Bus device [V3]

[Ian Campbell]

On Wed, 2013-07-03 at 09:34 +0100, Paul Durrant wrote:
> > -----Original Message-----
> > From: Ian Campbell
> > Sent: 03 July 2013 09:29
> > To: Stefano Stabellini
> > Cc: Paolo Bonzini; Paul Durrant; address@hidden; Anthony Liguori;
> > address@hidden
> > Subject: Re: [Xen-devel] [Qemu-devel] [PATCH] Citrix PV Bus device [V3]
> > 
> > On Tue, 2013-07-02 at 19:05 +0100, Stefano Stabellini wrote:
> > > On Tue, 2 Jul 2013, Stefano Stabellini wrote:
> > > > - the new device should have configurable vendor and device ids, so that
> > > > host admins can select which vendor's PV drivers are going to be
> > > > automatically installed on all your Windows guests. This should probably
> > > > be a VM config option (pvdevice=<gplpv|citrix|suse|oracle|etc>, libxl
> > would
> > > > then pass a vendor and device id pair to QEMU via command line.
> > > > We can come up with a config syntax that would support both numeric
> > > > pairs as well as simple labels.
> > >
> > > Anthony,
> > > would you be happy to have a PCI device in QEMU with configurable
> > vendor
> > > and device IDs?
> > 
> > IIRC there is also a revision field in the PCI config space. Might as
> > well make that configurable too.
> > 
> 
> Already did that  :-)
> 
> > There are also sub-vendor and sub-device IDs but I don't think they are
> > so useful for us (AFAIK they are intended to allow the board
> > manufacturer to "subclass" the IDs baked into the ASIC).
> > 
> 
> I'm always hazy about what those mean. I thought the idea was that a
> vendor may collect together many devices, potentially from different
> vendors, into a single chip/board and they should use common subsystem
> vendor/device info for all those devices to indicate that they were
> all part of that larger unit - but maybe I'm completely wrong.

I figured it was so the board vendor could add "value" in their drivers
by taking advantage of the higher precedence given to the binding to the
sub-ids by OSs.