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. > 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. > Specifically, I seek to allow low-latency user level network drivers (non > tcp/ip) which directly access SR-IOV style virtual network adapters, for use > with packages such as OpenMPI. > > Key areas of change: > - ioctl extensions to allow registration and dma mapping of memory regions, > with lock accounting > - support for mmu notifier driven de-mapping > - support for MSI and MSI-X interrupts (the intel 82599 VFs support only > MSI-X) > - allowing interrupt enabling and device register mapping all > through /dev/uio* so that permissions may be granted just by chmod > on /dev/uio* For non-priveledged users, we need a way to enforce that device is bound to an iommu. Further, locking really needs to be scoped with iommu domain existance and with iommu mappings: as long as a page is mapped in iommu, it must be locked. This patch does not seem to enforce that. Also note that what we really want is a single iommu domain per guest, not per device. 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 Thanks! -- MST -- 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
