Re: [Xen-devel] [PATCH 10/27] xen: make sure swiotlb allocation isphysically contigious

["Jan Beulich" <jbeulich@xxxxxxxxxx>]

>>> Jeremy Fitzhardinge <jeremy@xxxxxxxx> 13.03.09 17:59 >>>
> void * __init swiotlb_alloc_boot(size_t size, unsigned long nslabs)
> {
>-      return alloc_bootmem_low_pages(size);
>+      void *ret = alloc_bootmem_low_pages(size);
>+
>+      if (ret && xen_pv_domain())
>+              xen_swiotlb_fixup(ret, size, nslabs);
>+
>+      return ret;
> }
 
While on native using alloc_bootmem_low_pages() is a requirement here,
on Xen this should explicitly not be used, as we realized just a couple of
days ago: The way the bootmem allocator works, running out of space
below 4Gb is pretty easy on machines with lots of memory, and since the
swiotlb is a requirement for Dom0, the risk of allocation failures must be
kept as low as possible.

Jan


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