Re: [Linux-ia64] Re: [PATCH] head.S fix for unusual load addrs

Jack Steiner
2003-05-09T20:02:47Z

>
> >>>>> On Fri, 9 May 2003 10:52:25 -0700, Jesse Barnes <jbarnes@sgi.com> said:
>
> Jesse> So, is there any consensus on the best path to pursue? Chris Wedgwood
> Jesse> is working on option #3, and I've got Tony's patch trimmed down to #2
> Jesse> (with one piece missing--ia64_switch_to runtime patching), but none of
> Jesse> these are in either 2.4 or 2.5 yet. Maybe for 2.4 we should do #2 or
> Jesse> #3 and for 2.5 we could implement #1 with the virtual offsets Tony
> Jesse> mentioned earlier?
>
> I'm not sure. I got the impression Tony may be looking at the virtual
> remapping in region 5. I haven't heard whether text replication
> turned out to be important for 8870, but I'm starting to lean towards
> virtual remapping because it is more versatile (can handle both
> "strange" physical memory layouts and kernel replication). This,
> coupled with the fact that it doesn't break any of the existing tools
> makes it pretty compelling. Also, my primary objection about making
> the kernel model more complicated doesn't hold much water if we move
> everything to region 5.
>
> Would there be a downside to this on SGI's machines?

I dont see any significant problems. It actually seems easy.

I think we still need to use __tpa() for addresses assigned by the loader.
The standard __pa() macros wont work in region 5.

I dont have any objections to __tpa. We have had them in the kernel
since ~2.3.42 & have not had any problems with them. On occasion, when
we upgrade, we have to add/delete a couple of references but these are
always easy to find. I dont recall any changes for the last couple of upgrades
but maybe we were just lucky.

As I mention in mail earlier,

>> The __tpa macros are ugly but they are fully contained within the ia64 part
>> of the tree. (IIRC, the old scheduler had a reference but the O(1) scheduler doe not).
>> In our tree, there are currently only 12 references to __tpa. All are
>> in boottime initialization code, mostly in mca.c. Although I would
>> rather not have __tpa, this doesnt seem too bad.

>
> --david
>
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--
Thanks

Jack Steiner (651-683-5302) (vnet 233-5302) steiner@sgi.com