[+cc David, Logan, Alex, iommu list] On Thu, Aug 09, 2018 at 11:14:13AM -0700, Eric Pilmore wrote: > Didn't get any response on the IRC channel so trying here. > > Was wondering if anybody here has used IOAT DMA engines with an > IOMMU turned on (Xeon based system)? My specific question is really > whether it is possible to DMA (w/IOAT) to a PCI BAR address as the > destination without having to map that address to the IOVA space of > the DMA engine first (assuming the IOMMU is on)? So is this a peer-to-peer DMA scenario? You mention DMA, which would be a transaction initiated by a PCI device, to a PCI BAR address, so it doesn't sound like system memory is involved. I copied some folks who know a lot more about this than I do. > I am encountering issues where I see PTE Errors reported from DMAR > in this scenario, but I do not if I use a different DMA engine > that's sitting downstream off the PCI tree. I'm wondering if the > IOAT DMA failure is some artifact of these engines sitting behind > the Host Bridge. > > Thanks in advance! > Eric
