Re: adding /dev/xen/gnttab

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

On Thu, Sep 02, 2010 at 05:16:12PM +0200, Christoph Egger wrote:
> 
> > On Thu, Sep 02, 2010 at 04:00:44PM +0200, Christoph Egger wrote:
> > > 
> > > Hi!
> > > 
> > > For gnttab support a new device file is needed for a new set
> > > of ioctl()'s.
> > 
> > Can you explain what feature needs this gnttab device ?
> 
> Look at xentools33/patches/patch-aj
> 
> gnttab is needed
> a) to make xen tools compile
> b) for the grant table hypercalls in
>    sys/arch/xen/include/xen3-public/grant_table.h used by
>    xen tools
> c) for pci passthrough into HVM/PV guests
> d) for PV drivers in HVM guests
> d) for other things I'm not aware of

ok, thanks 

> [...]
> > > Attached patch adds /dev/xen/gnttab.
> > 
> > I see only patch for /dev/MAKEDEV, did you forget to
> > attach the diff for this device support ?
> 
> I implemented the stubs for NetBSD by adopting the Linux
> implementation. No, not for xen 3.3 but for xen-unstable
> which is heading to Xen 4.1.
> 
> The kernel side is not yet written.
> I just want to have the device file as a first step.

I don't think it's approrpiate to commit this patch before the
kernel side is written then. they should be commited as a whole.
this doesn't prevent you from moving existing devices to /dev/xen though.


> 
> > > I would like to use the opportunity to move xen device files
> > > into /dev/xen/. The patch keeps the existing ones for backward
> > > compatibility.
> > 
> > Looks good to me.
> 
> Thanks. Oh, do you mind if I add privcmd to /dev/xen/ as well?
> The kernel code to use /dev/xen/privcmd should be easy to adopt
> and will finally allow to remove kernfs.

I don't think kernfs can be removed. it's needed for dynamic entries
like /kern/xen/pci. I'm not sure xsd_port can be supported as a device
either.

-- 
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference
--