On Wed, May 20, 2015 at 03:15:59PM -0400, Mark Hounschell wrote: > On 05/20/2015 01:30 PM, William Davis wrote: > >In an IOMMU environment, the DMA ops would be one of the IOMMU > >implementations, so these APIs would create a mapping for the peer device > >resource, even if it's on the same bus. Would a transaction targeting that > >mapping be forwarded upstream until it hits an IOMMU, which would then send > >the translated request back downstream? Or is my understanding of this > >configuration incorrect? > > > > It's my understanding of the IOMMU that is lacking here. I have no > idea if that is actually what would happen. Does it? On the x86 side at least the IOMMU drivers enable ACS when available, forcing all perr-to-peer DMA between PCIe devices to go through the IOMMU. This only works when the peers are in different iommu groups, though. Joerg -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
