Re: x86_64: 2.6.14-rc4 swiotlb broken

[Muli Ben-Yehuda <mulix@mulix.org>]

On Mon, Oct 17, 2005 at 05:40:56PM +0200, Andi Kleen wrote:

> First this problem is definitely not critical. AFAIK it only happens on 
> scalex's unreleased machines. Intel NUMA x86 machines are really rare
> and on AMD it doesn't happen because the swiotlb is not used there.

It's not used by default, but there are cases where it's used and it
would be a shame to release a major kernel and knowingly break
them. For example, any setup that used iommu_force or any non-AMD
x86-64 machine with more than 4GB of memory and only 32-bit capable
DMA devices.

> Both NODE(0) and node_online_map are risky. NODE(0) may break IA64
> (they share this code) and node_online_map may break one of the weirder
> ARM platforms again (for which the original revert was done)

I don't have an IA64 machine, but if the NODE(0) fix is safe there, I
vote for it for 2.6.14-rc4. Another alternative is to temporarily
provide a different version of swiotlb_init() for x86-64 and IA64 -
I can whip up a patch if that's acceptable.

Cheers,
Muli
-- 
Muli Ben-Yehuda
http://www.mulix.org | http://mulix.livejournal.com/

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