Re: [PATCH] disable CPU side GART accesses

Dave Airlie
2008-10-29T21:24:46Z

On Thu, Oct 30, 2008 at 6:52 AM, Bob Montgomery <bob.montgomery@hp.com> wrote:
> On Mon, 2008-10-27 at 23:06 +0000, Yinghai Lu wrote:
>> Bob Montgomery wrote:
>> > On Wed, 2008-10-15 at 23:48 +0000, Ingo Molnar wrote:
>> >> (Cc:-ed the GART folks.)
>> >
>> > Are there any objections to this patch? The problem has been reproduced
>> > in 2.6.18 and 2.6.27, so existing changes in the gart code have not
>> > addressed it.
>>
>> better to have someone with amd system + 8g ram + agp adapter to verify it...
>>
>> YH
>
> Good idea.
>
> I don't think HP made a system with opteron and agp, so I haven't found
> a system here to test. But I did see that there have been non-HP
> motherboards from several years ago that advertised opteron with agp.
> Anyone running that type of system?
>
> The other question is whether AGP graphics on linux for amd64 ever
> expected host translation to work, since setting DisGartCpu is turning
> off host translation.

We have an option in the AGP drivers called cant_use_aperture.

This stops the CPU from using the aperture for most DRI things. I
can't confirm this won't regress working systems
though. The whole AMD GART thing scares me, esp if some of the host
chipsets also have an AGP GART.

Dave.