Re: [PATCH v1 2/2] dma-mapping-common: add DMA attribute - DMA_ATTR_IOMMU_BYPASS

Arnd Bergmann
2015-11-02T21:45:54Z

On Tuesday 03 November 2015 07:13:28 Benjamin Herrenschmidt wrote:
> On Mon, 2015-11-02 at 14:07 +0200, Shamir Rabinovitch wrote:
> > On Mon, Nov 02, 2015 at 09:00:34PM +1100, Benjamin Herrenschmidt
> > wrote:
> > >
> > > Chosing on a per-mapping basis *in the back end* might still make
> > > some
> >
> > In my case, choosing mapping based on the hardware that will use this
> > mappings makes more sense. Most hardware are not that performance
> > sensitive as the Infiniband hardware.
>
> ...
>
> > The driver know for what hardware it is mapping the memory so it know
> > if the memory will be used by performance sensitive hardware or not.
>
> Then I would argue for naming this differently. Make it an optional
> hint "DMA_ATTR_HIGH_PERF" or something like that. Whether this is
> achieved via using a bypass or other means in the backend not the
> business of the driver.
>

With a name like that, who wouldn't pass that flag? ;-)

Arnd