On Thu, 2012-09-13 at 17:41 -0500, Scott Wood wrote: > On Thu, Sep 13, 2012 at 04:34:59PM -0600, Alex Williamson wrote: > > Do you only want VFIO drivers to work on POWER if they're written by > > POWER people? Ideally there are a few simple concepts: a) devices have > > an I/O virtual address space. On x86 we call this the iova and it's > > effectively a zero-based, 64bit (not really, but close enough) address > > space. You seem to have two smaller windows, one in 32bit space, > > another in 64bit space (maybe we could name these more consistently). > > b) Userspace has a buffer that they want to map and unmap to an iova, > > potentially with some access flags. That's all you need to know to use > > the x86 _type1 VFIO IOMMU API. Why do I need to know about H_PUT_TCE to > > use this interface? Let's assume there might be some VFIO drivers some > > day that aren't written by POWER people. Thanks, > > I'm not familiar with the POWER IOMMU, but certainly with our chips it > would help allow generic drivers to work if there were a type of mapping > operation where the IOMMU driver decides the IOVA and returns it, instead > of the driver trying to choose the IOVA with no knowledge of the IOMMU's > constraints.
That sounds reasonable to me. If we had IOMMU API support for that in the kernel on x86, it would only take an ALLOC_IOVA flag in the MAP ioctl, returning the iova in the mapping structure, and the addition of a capability to let userspace know it's there. Thanks, Alex _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
