Re: [Xen-devel] Failure to get memory for GATT table, again

[Ian Pratt <Ian.Pratt@xxxxxxxxxxxx>]

> > The AGP aperture needs a set of machine contiguous pages, whereas
> > get_free_pages will only give you pseudo-physical contiguous.
> > 
> > Drivers are supposed to use the former (for reasons of ensuring
> > DMA coherence) , but the agp drivers seem particularly shoddy,
> > probably because they've only ever been used on x86.
> 
> Hmm but it seems that dev->dma_mem is never set for the device, causing a 
> fallback to
> __get_free_pages(). Should the driver have set this?

dma_alloc_coherent allocates some pages, then calls
xen_contig_memory which swaps them for machine contiguous ones.

You should be able to call ioremap_nocache on the virt_to_bus'ed
address you get back from xen_contig_memory.

Ian


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