Re: [Xen-devel] Xen 3.0 Status update

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 29 Jul 2005, at 10:06, Gerd Knorr wrote:

> DMA memory really can be almost anything.  There is no way around
> having a swiotlb-like bounce buffer mechanism hooked into the dma
> mapping API as fallback.
>
> At the moment the linux kernel provides no way to hint that you want
> to use the specific piece of memory you are asking for for 32-bit PCI
> DMA.  ZONE_DMA is historical stuff, 16MB only for ISA DMA IIRC, not
> really useful.  Maybe Andy finally finds some time to polish & submit
> the ZONE_DMA32 patch.
Any driver that really wants ZONE_DMA memory on xenlinux (ie. 24-bit 
safe memory) is screwed. The low 16MB memory is always allocated 
exclusively to Xen itself.
That does only affect old ISA hardware though, afaik.

 -- Keir



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