tree d6303358532275cd114b471810d6fc2333780367
parent fff5d99225107f5f13fe4a9805adc2a1c4b5fb00
author Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> 1482246122 -0500
committer Konrad Rzeszutek Wilk <konrad@kernel.org> 1483725601 -0500

swiotlb: Export swiotlb_max_segment to users

So they can figure out what is the optimal number of pages
that can be contingously stitched together without fear of
bounce buffer.

We also expose an mechanism for sub-users of SWIOTLB API, such
as Xen-SWIOTLB to set the max segment value. And lastly
if swiotlb=force is set (which mandates we bounce buffer everything)
we set max_segment so at least we can bounce buffer one 4K page
instead of a giant 512KB one for which we may not have space.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reported-and-Tested-by: Juergen Gross <jgross@suse.com>