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    SubjectRe: [PATCH 0/1] uio_pci_generic: extensions to allow access for non-privileged processes
    On Thu, Apr 01, 2010 at 08:40:34AM -0700, Tom Lyon wrote:
    > On Thursday 01 April 2010 05:52:18 am Joerg Roedel wrote:

    > > > The point of this patch is to beef up the uio_pci_generic driver so that
    > > > a non-privileged user process can run a user level driver for most PCIe
    > > > devices. This can only be safe if there is an IOMMU in the system with
    > > > per-device domains. Privileged users (CAP_SYS_RAWIO) are allowed if
    > > > there is no IOMMU.
    > >
    > > If you rely on an IOMMU you can use the IOMMU-API instead of the DMA-API
    > > for dma mappings. This change makes this driver suitable for KVM use
    > > too. If the interface is designed clever enough we can even use it for
    > > IOMMU emulation for pass-through devices.

    > The use with privileged processes and no IOMMUs is still quite useful, so I'd
    > rather stick with the DMA interface.

    For the KVM use-case we need to be able to specify the io virtual
    address for a given process virtual address. This is not possible with
    the dma-api interface. So if we want to have uio-dma without an hardware
    iommu we need two distinct interfaces for userspace to cover all
    use-cases. I don't think its worth it to have two interfaces.


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