[Xen-ia64-devel] RE: PG_arch_1 conflict

["Magenheimer, Dan (HP Labs Fort Collins)" <dan.magenheimer@xxxxxx>]

See previous discussion at:

http://lists.xensource.com/archives/html/xen-devel/2005-12/msg00238.html


The issue is that PG_arch_1 is reserved for arch-specific
usage, the paravirtualization changes for Xenlinux utilize
it (to mark foreign pages) because it was otherwise unused
in Linux/x86.  But Xen is no longer an arch.

Grep'ing for "PageForeign" in -sparse will show most (all?)
of the actual uses of it.  Nearly all are in x86-specific
code.  But one is in netback_init().

Dan

> -----Original Message-----
> From: Hollis Blanchard [mailto:hollisb@xxxxxxxxxx] 
> Sent: Friday, March 10, 2006 1:38 PM
> To: Magenheimer, Dan (HP Labs Fort Collins)
> Cc: xen-ia64-devel@xxxxxxxxxxxxxxxxxxx; Keir Fraser; 
> xen-ppc-devel@xxxxxxxxxxxxxxxxxxx
> Subject: Re: PG_arch_1 conflict
> 
> Magenheimer, Dan (HP Labs Fort Collins) wrote:
> > We're not quite to the point of bringing up networking
> > yet but in digging through the mailing list archive,
> > I was reminded of a problem that we will soon run into:
> > Xenlinux/x86 utilizes the PG_arch_1 bit to represent
> > a "foreign" page.  Linux/ia64 (and I think Linux/ppc)
> > use the PG_arch_1 bit for arch-dep purposes.
> > 
> > It this conflict is not resolved before Xenlinux/ia64
> > supports networking, there will likely be some very
> > interesting bugs...
> 
> What is the actual issue here? Where is the code dealing with 
> PG_arch_1?
> 
> -- 
> Hollis Blanchard
> IBM Linux Technology Center
> 

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