On Wed, Aug 31, 2011 at 12:56:26PM -0400, Laurent Pinchart wrote: > True, but if we implement address rounding transparently in the IOMMU layer > Ohad's concern can be valid, depending on whether the device is trusted. If we > decide to push address rounding to the drivers that decision can be made on a > per-device basis. However, drivers are usually not aware of what granularity > the IOMMU works on, so that wouldn't be straightforward and clean. Drivers usually just use the DMA-API, so they can not assume at all that any protection happens. The problem also can't be really solved without changing/breaking the DMA-API. It is defined to work on byte granularity while the hardware only works with pages. The only way to work around this it to implement the driver in a way so that they only map page-aligned buffers where the size is also a multiple of a page-size. In this case you can assume the page-size you are working on because you already assume in the driver that an iommu is in use. Joerg -- AMD Operating System Research Center Advanced Micro Devices GmbH Einsteinring 24 85609 Dornach General Managers: Alberto Bozzo, Andrew Bowd Registration: Dornach, Landkr. Muenchen; Registerger. Muenchen, HRB Nr. 43632 -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
