Messages in this thread | | | Date | Thu, 1 Apr 2010 18:07:47 +0200 | From | Joerg Roedel <> | Subject | Re: [PATCH 0/1] uio_pci_generic: extensions to allow access for non-privileged processes |
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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.
Joerg
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