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. > In your case, what will give the better performance - 1:1 mapping or > IOMMU > mapping? When you say 'relaxing the protection' you refer to 1:1 > mapping? > Also, how this 1:1 window address the security concerns that other > raised > by other here? It will partially only but it's just an example of another way the bakcend could provide some improved performances without a bypass. Cheers, Ben. -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
