Subject: Re: remplacing page mappings behind uvm
To: YAMAMOTO Takashi <yamt@mwd.biglobe.ne.jp>
From: Manuel Bouyer <bouyer@antioche.eu.org>
List: tech-kern
Date: 11/30/2007 17:19:50
On Sat, Dec 01, 2007 at 01:05:27AM +0900, YAMAMOTO Takashi wrote:
> > > RCS file: /cvsroot/pkgsrc/sysutils/xentools20/patches/patch-as,v
> > > 
> > > ----------------------------
> > > revision 1.1
> > > date: 2005/05/23 22:02:04;  author: bouyer;  state: Exp;
> > > branches:  1.1.2;
> > > Don't mmap /kern/xen/privcmd (this doesn't work any more on current), use
> > > MAP_ANON instead. Bump pkgrevision.
> > > ----------------------------
> > 
> > But this is Xen2, not Xen3 ... I think this was in a different context, not
> > related to the IOCTL_PRIVCMD_MMAP* ioctls.
> 
> they are for IOCTL_PRIVCMD_MMAPBATCH/IOCTL_PRIVCMD_MMAP.

Yes, but in Xen2. They're not used in exactly the same way in Xen3.

> 
> > In xen3, this happens in libxc/xc_netbsd.c. We have to implement a
> > xc_map_foreign_range() function, which has to map memory from a remote
> > domain over an existing VA range. xc_map_foreign_range() doesn't allocate
> > the VA space itself (eventually the same VA range will be remapped several
> > times).
> > 
> > I suspect this is exported to python ...
> 
> libxc mmap /proc/xen/privcmd for linux.

But this doesn't helps us, because it's mmapped before calling
IOCTL_PRIVCMD_MMAP*. AFAIK we have to return a valid page address at the
time a device mmap callback is called.

-- 
Manuel Bouyer, LIP6, Universite Paris VI.           Manuel.Bouyer@lip6.fr
     NetBSD: 26 ans d'experience feront toujours la difference
--