lkml.org 
[lkml]   [2018]   [Apr]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [LSF/MM TOPIC NOTES] x86 ZONE_DMA love
On Fri, Apr 27, 2018 at 11:36:23AM -0500, Christopher Lameter wrote:
> On Fri, 27 Apr 2018, Matthew Wilcox wrote:
>
> > Some devices have incredibly bogus hardware like 28 bit addressing
> > or 39 bit addressing. We don't have a good way to allocate memory by
> > physical address other than than saying "GFP_DMA for anything less than
> > 32, GFP_DMA32 (or GFP_KERNEL on 32-bit) for anything less than 64 bit".
> >
> > Even CMA doesn't have a "cma_alloc_phys()". Maybe that's the right place
> > to put such an allocation API.
>
> The other way out of this would be to require a IOMMU?

Which on many systems doesn't exist. And even if it exists might not
be usable.

\
 
 \ /
  Last update: 2018-04-28 10:34    [W:0.050 / U:1.276 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site