On Tue, Nov 03, 2020 at 02:18:52PM +0100, joro@xxxxxxxxxx wrote: > On Tue, Nov 03, 2020 at 08:56:43AM -0400, Jason Gunthorpe wrote: > > On Tue, Nov 03, 2020 at 10:52:09AM +0100, joro@xxxxxxxxxx wrote: > > > So having said this, what is the benefit of exposing those SVA internals > > > to user-space? > > > > Only the device use of the PASID is device specific, the actual PASID > > and everything on the IOMMU side is generic. > > > > There is enough API there it doesn't make sense to duplicate it into > > every single SVA driver. > > What generic things have to be done by the drivers besides > allocating/deallocating PASIDs and binding an address space to it? > > Is there anything which isn't better handled in a kernel-internal > library which drivers just use? Userspace needs fine grained control over the composition of the page table behind the PASID, 1:1 with the mm_struct is only one use case. Userspace needs to be able to handle IOMMU faults, apparently The Intel guys had a bunch of other stuff too, looking through the new API they are proposing for vfio gives some flavour what they think is needed.. Jason
