Re: 32-bit dma allocations on 64-bit platforms

David Mosberger
2004-06-26T04:59:08Z

>>>>> On Thu, 24 Jun 2004 20:51:56 +0200, Andi Kleen <ak@muc.de> said:

Andi> A better IO_TLB_SHIFT would be 16 or 17.

Careful. I see code like this:

stride = (1 << (PAGE_SHIFT - IO_TLB_SHIFT));

You probably don't want IO_TLB_SHIFT > PAGE_SHIFT... Increasing
io_tlb_nslabs should be no problem though (subject to memory
availability). It can already by set via the "swiotlb" option.

I doubt swiotlb is the right thing here, though, given the bw-demands
of graphics. Too bad Nvidia cards don't support > 32 bit
addressability and Intel chipsets don't support I/O MMUs...

--david