Re: [Xen-devel] [PATCH 1/9] xen: make sure swiotlb allocation isphysically contigious

[Jan Beulich]

>>> Jeremy Fitzhardinge <jeremy@xxxxxxxx> 08.05.09 02:17 >>>
>Impact: make swiotlb allocation suitable for Xen
>
>When allocating the swiotlb buffer under Xen, make sure the memory is
>physically contiguous so that its really suitable for DMA.
>
>Do this by allocating the memory as usual, but then call a Xen
>function to rearrange the underlying pages to be physically
>contiguous.

As pointed out before, you must not use alloc_bootmem_low...() here,
as on large systems you may otherwise get an allocation failure (i.e. a
panic - checking the return value is pointless). The alternative is to fix
the bootmem allocator to no longer allocate from bottom up.

Jan

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