Re: Linux PG_arch_1 conflict

Re: Linux PG_arch_1 conflict

[Hollis Blanchard]

Magenheimer, Dan (HP Labs Fort Collins) wrote:
> 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().

That thread seems to already have a solution. Has anybody run it past 
Linux MM people? (Adding xen-devel to CC for greater exposure.)

-- 
Hollis Blanchard
IBM Linux Technology Center

RE: Linux PG_arch_1 conflict

[Magenheimer, Dan (HP Labs Fort Collins)]

>
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().
> 
> That thread seems to already have a solution. Has anybody run it past 
> Linux MM people? (Adding xen-devel to CC for greater exposure.)

If by "solution" you mean that Keir could change Xenlinux to
add a new "PG_foreign" bit and change Xenlinux/x86 (and netback)
to use that bit rather than PG_arch_1, I agree.

Comments, Keir (or others)?

Dan

Re: Linux PG_arch_1 conflict

[Keir Fraser]

On 10 Mar 2006, at 21:11, Magenheimer, Dan (HP Labs Fort Collins) wrote:

>> That thread seems to already have a solution. Has anybody run it past
>> Linux MM people? (Adding xen-devel to CC for greater exposure.)
>
> If by "solution" you mean that Keir could change Xenlinux to
> add a new "PG_foreign" bit and change Xenlinux/x86 (and netback)
> to use that bit rather than PG_arch_1, I agree.
>
> Comments, Keir (or others)?

Sounds like the proper fix. I'll leave it to Christian and others 
involved in the Linux upstreaming effort to have the final word.

  -- Keir

RE: Linux PG_arch_1 conflict

[Magenheimer, Dan (HP Labs Fort Collins)]

> On 10 Mar 2006, at 21:11, Magenheimer, Dan (HP Labs Fort 
> Collins) wrote:
> 
> >> That thread seems to already have a solution. Has anybody 
> run it past
> >> Linux MM people? (Adding xen-devel to CC for greater exposure.)
> >
> > If by "solution" you mean that Keir could change Xenlinux to
> > add a new "PG_foreign" bit and change Xenlinux/x86 (and netback)
> > to use that bit rather than PG_arch_1, I agree.
> >
> > Comments, Keir (or others)?
> 
> Sounds like the proper fix. I'll leave it to Christian and others 
> involved in the Linux upstreaming effort to have the final word.

Comments, Christian (or others)?  Any chance this will get into
3.0.2?  Certainly it should be changed before attempting to push
the drivers upstream to Linux.