On Mon, 5 Feb 2018 15:58:22 +0200 Ran Shalit <ranshalit@xxxxxxxxx> wrote: > Hello, > > > I can't find in uio_pci_generic.c any usage of DMA. > Is it that the driver does not use DMA in transactions between device > and host ? If not - isn't it a sort disadvantage ? AIUI, uio_pci_generic doesn't officially support DMA because there's no way that a userspace driver can safely support DMA without an IOMMU isolating the device. Otherwise the userspace driver can use the device to read and write data anywhere it wants, which is also sort of a disadvantage. Of course this doesn't seem to stop anyone from doing DMA with uio_pci_generic, but you're not likely to get much support for such uses. Instead, you might want to be looking at vfio, which does make use of (and require) IOMMU support in order to more safely allow userspace drivers to use DMA. Thanks, Alex
