On Sat, 27 Feb 2010 12:15:19 -0600 Robert Hancock <hancockrwd@xxxxxxxxx> wrote: > On Sat, Feb 27, 2010 at 6:05 AM, David Miller <davem@xxxxxxxxxxxxx> wrote: > > From: Bartlomiej Zolnierkiewicz <bzolnier@xxxxxxxxx> > > Date: Sat, 27 Feb 2010 12:59:31 +0100 > > > >> Having IOMMU (even if it is only a software one, i.e. this would > >> mean swiotlb for x86-32/highmem) always in place would simplify > >> things greatly.. > > > > I agree, things would be a lot simpler. > > Yeah, the situation kind of sucks on the platforms that don't have any > IOMMU support, since it means that the DMA API can't handle anything > over 4GB properly and you need all these hacks in the block layer, > networking layer, etc. It would be nice if some kind of IOMMU support > could be relied upon always. When I proposed such approach (always use swiotlb) before, IIRC, the objections were: - better to make allocation respect dma_mask. (I don't think that this approach is possible since we don't know which device handles data later when we allocate memory). - swiotlb is not good for small systems since it allocates too much memory (we can fix this though). There might be more. -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
