[Xen-devel] Re: [Patch] Constrain DMADOM/swiotlb allocations to 1G phys to fix b44 NIC driver

["Stephen C. Tweedie" <sct@xxxxxxxxxx>]

Hi,

On Tue, 2006-11-28 at 15:46 +0000, Stephen C. Tweedie wrote:

> It turns out that this 2GB / 31-bit constraint is magically hardcoded in
> a couple of places rather than being read correctly from config.h.  So
> this patch fixes that; changes config.h to specify a 1GB / 30-bit
> constraint for the DMADOM heap; and changes the x86/x86_64 swiotlb to
> request a 30-bit constraint for allocations of the swiotlb memory.

The 30 bit constraint is enough to let b44 work.  But there are a number
of sound cards which require a 28-bit DMA mask (256MB max physical
addressable memory).  1GB seems reasonably safe, but I'm much less
comfortable with restricting DMADOM to 256MB by default.  Does anyone
have any strong feelings about shifting this?  What other users of
DMADOM are there that might overflow if we restrict it even further?

Cheers,
 Stephen



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