Messages in this thread | | | Date | Mon, 17 Jun 2002 01:37:32 +0200 | From | Andi Kleen <> | Subject | Re: another new version of pageattr caching conflict fix for 2.4 |
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> > MTRRs work on physical, not virtual memory, so they have no aliasing > > issues. > > Doesn't the AGP aperture cause a physical alias? Leading to strange
Yes. That's what this patch is all about.
> the same problems if the agp aperture was marked write-back, and the
AGP aperture is uncacheable, not write-back.
> memory was marked uncacheable. My gut impression is to just make the > agp aperture write-back cacheable, and then we don't have to change > the kernel page table at all. Unfortunately I don't expect the host
That would violate the AGP specification.
> bridge with the memory and agp controllers to like that mode, > especially as there are physical aliasing issues.
exactly.
> > > Fixing the MTRRs is fine, but it is really outside the scope of my patch. > > Just changing the kernel map wouldn't be enough to fix wrong MTRRs, > > because it wouldn't cover highmem. > > My preferred fix is to use PAT, to override the buggy mtrrs. Which > brings up the same aliasing issues. Which makes it related but > outside the scope of the problem.
I don't follow you here. IMHO it is much easier to fix the MTRRs in the MTRR driver for those rare buggy BIOS (if they exist - I've never seen one) than to hack up all of memory management just to get the right bits set. I see no disadvantage of using the MTRRs and it is lot simpler than PAT and pte bits.
-Andi
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