On Tue, 11 Nov 2025 06:52:01 -0800 Alex Mastro <[email protected]> wrote:
> Not all IOMMUs support the same virtual address width as the processor, > for instance older Intel consumer platforms only support 39-bits of > IOMMU address space. On such platforms, using the virtual address as > the IOVA and mappings at the top of the address space both fail. > > VFIO and IOMMUFD have facilities for retrieving valid IOVA ranges, > VFIO_IOMMU_TYPE1_INFO_CAP_IOVA_RANGE and IOMMU_IOAS_IOVA_RANGES, > respectively. These provide compatible arrays of ranges from which > we can construct a simple allocator and record the maximum supported > IOVA address. > > Use this new allocator in place of reusing the virtual address, and > incorporate the maximum supported IOVA into the limit testing. This > latter change doesn't test quite the same absolute end-of-address space > behavior but still seems to have some value. Testing for overflow is > skipped when a reduced address space is supported as the desired errno > is not generated. > > This series is based on Alex Williamson's "Incorporate IOVA range info" > [1] along with feedback from the discussion in David Matlack's "Skip > vfio_dma_map_limit_test if mapping returns -EINVAL" [2]. > > Given David's plans to split IOMMU concerns from devices as described in > [3], this series' home for `struct iova_allocator` and IOVA > range helpers are likely to be short lived, since they reside in > vfio_pci_device.c. I assume that the rework can move this functionality > to a more appropriate location next to other IOMMU-focused code, once > such a place exists. > > [1] https://lore.kernel.org/all/[email protected]/#t > [2] https://lore.kernel.org/all/[email protected]/ > [3] https://lore.kernel.org/all/[email protected]/ > > To: Alex Williamson <[email protected]> > To: David Matlack <[email protected]> > To: Shuah Khan <[email protected]> > To: Jason Gunthorpe <[email protected]> > Cc: [email protected] > Cc: [email protected] > Cc: [email protected] > Signed-off-by: Alex Mastro <[email protected]> > > Changes in v2: > - Fix various nits > - calloc() where appropriate > - Update overflow test to run regardless of iova range constraints > - Change iova_allocator_init() to return an allocated struct > - Unfold iova_allocator_alloc() > - Fix iova allocator initial state bug > - Update vfio_pci_driver_test to use iova allocator > - Link to v1: > https://lore.kernel.org/r/[email protected] Minor comments, but otherwise LGTM and passes testing on a Kaby Lake system with limited IOMMU address width. Thanks, Alex
