From: Grant Grundler <iod00d@hp.com>
To: linux-ia64@vger.kernel.org
Subject: Re: Queries on IA -64
Date: Mon, 16 May 2005 16:43:25 +0000 [thread overview]
Message-ID: <20050516164325.GC29357@esmail.cup.hp.com> (raw)
In-Reply-To: <20050516114921.28015.qmail@web54008.mail.yahoo.com>
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
next prev parent reply other threads:[~2005-05-16 16:43 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-05-16 11:49 Queries on IA -64 Mohit Katiyar
2005-05-16 16:43 ` Grant Grundler [this message]
2005-05-17 23:05 ` Bjorn Helgaas
2005-05-18 5:18 ` Mohit Katiyar
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