On Thu, Apr 01, 2010 at 05:25:04PM +0300, Michael S. Tsirkin wrote: > On Wed, Mar 31, 2010 at 05:08:38PM -0700, Tom Lyon wrote: > > uio_pci_generic has previously been discussed on the KVM list, but this patch > > has nothing to do with KVM, so it is also going to LKML. > > > > 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. > > Why? Per-guest domain should be safe enough. Hardware IOMMUs don't have something like a per-guest domain ;-) Anyway, if we want to emulate an IOMMU in the guest and make this working for pass-through devices too we need more than one domain per guest. Essentially we may need one domain per device. > > Privileged users (CAP_SYS_RAWIO) are allowed if there is > > no IOMMU. > > qemu does not support it, I doubt this last option is worth having. Agreed. > For this reason, I think we should address the problem somwwhat > differently: > - Create a character device to represent the iommu > - This device will handle memory locking etc > - Allow binding this device to iommu > - Allow other operations only after iommu is bound Yes, something like this is needed. But I think we can implement this in the generic uio-pci-driver. A seperate interface which basically passes the iommu-api functions to userspace doesn't make sense because it would also be device-centric like the uio-pci-driver. Joerg -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
