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Re: [Xen-devel] Xen 3.0 Status update

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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