Hi Pierre, On 18/01/2019 13:29, Pierre Morel wrote: > On 17/01/2019 14:02, Robin Murphy wrote: >> On 15/01/2019 17:37, Pierre Morel wrote: >>> The s390 iommu can only allow DMA transactions between the zPCI device >>> entries start_dma and end_dma. >>> >>> Let's declare the regions before start_dma and after end_dma as >>> reserved regions using the appropriate callback in iommu_ops. >>> >>> The reserved region may later be retrieved from sysfs or from >>> the vfio iommu internal interface. >> >> For this particular case, I think the best solution is to give VFIO >> the ability to directly interrogate the domain geometry (which s390 >> appears to set correctly already). The idea of reserved regions was >> really for 'unexpected' holes inside the usable address space - using >> them to also describe places that are entirely outside that address >> space rather confuses things IMO. >> >> Furthermore, even if we *did* end up going down the route of actively >> reserving addresses beyond the usable aperture, it doesn't seem >> sensible for individual drivers to do it themselves when the core API >> already describes the relevant information generically. >> >> Robin. > > Robin, > > I already posted a patch retrieving the geometry through > VFIO_IOMMU_GET_INFO using a specific capability for the geometry [1], > and AFAIU, Alex did not agree with this. On arm we also need to report the IOMMU geometry to userspace (max IOVA size in particular). Shameer has been working on a solution [2] that presents a unified view of both geometry and reserved regions into the VFIO_IOMMU_GET_INFO call, and I think we should go with that. If I understand correctly it's currently blocked on the RMRR problem and we're waiting for Jacob or Ashok to take a look at it, as Kevin pinged them on thread [1]? [2] https://lkml.org/lkml/2018/4/18/293 Thanks, Jean > > What is different in what you propose? > > @Alex: I was hoping that this patch goes in your direction. What do you > think? > > Thanks, > Pierre > > [1]: https://lore.kernel.org/patchwork/patch/1030369/ > >> >>> >>> This seems to me related with the work Shameer has started on >>> vfio_iommu_type1 so I add Alex and Shameer to the CC list. >>> >>> >>> Pierre Morel (1): >>> iommu/s390: Declare s390 iommu reserved regions >>> >>> drivers/iommu/s390-iommu.c | 29 +++++++++++++++++++++++++++++ >>> 1 file changed, 29 insertions(+) >>> >> > >
