Re: [PATCH] x86: mtrr cleanup for converting continuous to discrete layout v2

[Mika Fischer <mika.fischer@zoopnet.de>]

Arjan van de Ven schrieb:
> yep one should not touch existing MTRRs. If you run out, tough luck.
> Thats what we have PAT for.
> Changing them anyway is a deathtrap with various things, suspend/resume being only
> one of the nasty cases.

Hm. I currently have to remove the offending (i.e. overlapping my video
memory) MTRRs and split them so that they have a hole where my video
memory is.

Only that makes the X server happy, which wants to set up a
write-combining range covering the video memory.

Is there a better workaround?

>> how relevant is this feature with modern Xorg? I thought modern Xorg 
>> would get its mappings via /sys, hence it would not have to touch
>> MTRRs at all.
> 
> that's true for current X, but not for 6 month old X :=(

Ah, so the new X will be able to use the video memory in write-combining
mode even if I have an MTRR saying this area is uncachable or write-back?

If that is the case, then I agree that this patch is not really needed.

Regards,
 Mika