Re: Queries on IA -64

From: Grant Grundler <iod00d_at_hp.com>
Date: 2005-05-17 02:43:25
On Mon, May 16, 2005 at 04:49:20AM -0700, Mohit Katiyar wrote:
> Hi,
> I am first time mailing regarding some booting
> procedure for IA-64 Linux . I am having a ZX MIO chip
> with 6 GB RAM and 16 KB of page size. I have compiled
> the kernel with NUMA off and Virtual mem map on
> 
> First in function paging_init 
> line    max_dma = virt_to_phys((void *)
> MAX_DMA_ADDRESS) >> PAGE_SHIFT;
> max_dma comes out to be 0x7fffffffffff and max low pfn
> = 0x103ffec
> Therefore all the pages move into DMA zone during
> initialization .
> QUESTION Why do we have such a large max_dma value.
> What is the use for that?

Avoid bounce buffers and support IOMMU bypass.
Any device can DMA to any physical address - either
directly or via IOMMU.

grant
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Received on Mon May 16 12:41:41 2005

This archive was generated by hypermail 2.1.8 : 2005-08-02 09:20:39 EST