Ping.
On Fri, Dec 18, 2020 at 12:36:00AM +0530, Nithin Dabilpuram wrote: > Partial DMA unmap is not supported by VFIO type1 IOMMU > in Linux. Though the return value is zero, the returned > DMA unmap size is not same as expected size. > So add test case and fix to both heap triggered DMA > mapping and user triggered DMA mapping/unmapping. > > Refer vfio_dma_do_unmap() in drivers/vfio/vfio_iommu_type1.c > Snippet of comment is below. > > /* > * vfio-iommu-type1 (v1) - User mappings were coalesced together to > * avoid tracking individual mappings. This means that the > granularity > * of the original mapping was lost and the user was allowed to > attempt > * to unmap any range. Depending on the contiguousness of physical > * memory and page sizes supported by the IOMMU, arbitrary unmaps may > * or may not have worked. We only guaranteed unmap granularity > * matching the original mapping; even though it was untracked here, > * the original mappings are reflected in IOMMU mappings. This > * resulted in a couple unusual behaviors. First, if a range is not > * able to be unmapped, ex. a set of 4k pages that was mapped as a > * 2M hugepage into the IOMMU, the unmap ioctl returns success but > with > * a zero sized unmap. Also, if an unmap request overlaps the first > * address of a hugepage, the IOMMU will unmap the entire hugepage. > * This also returns success and the returned unmap size reflects the > * actual size unmapped. > > * We attempt to maintain compatibility with this "v1" interface, but > > * we take control out of the hands of the IOMMU. Therefore, an > unmap > * request offset from the beginning of the original mapping will > > * return success with zero sized unmap. And an unmap request > covering > * the first iova of mapping will unmap the entire range. > > > This behavior can be verified by using first patch and add return check for > dma_unmap.size != len in vfio_type1_dma_mem_map() > > v6: > - Fixed issue with x86-32 build introduced by v5. > > v5: > - Changed vfio test in test_vfio.c to use system pages allocated from > heap instead of mmap() so that it comes in range of initially configured > window for POWER9 System. > - Added acked-by from David for 1/4, 2/4. > > v4: > - Fixed issue with patch 4/4 on x86 builds. > > v3: > - Fixed external memory test case(4/4) to use system page size > instead of 4K. > - Fixed check-git-log.sh issue and rebased. > - Added acked-by from anatoly.bura...@intel.com to first 3 patches. > > v2: > - Reverted earlier commit that enables mergin contiguous mapping for > IOVA as PA. (see 1/3) > - Updated documentation about kernel dma mapping limits and vfio > module parameter. > - Moved vfio test to test_vfio.c and handled comments from > Anatoly. > > Nithin Dabilpuram (4): > vfio: revert changes for map contiguous areas in one go > vfio: fix DMA mapping granularity for type1 IOVA as VA > test: add test case to validate VFIO DMA map/unmap > test: change external memory test to use system page sz > > app/test/meson.build | 1 + > app/test/test_external_mem.c | 3 +- > app/test/test_vfio.c | 107 > +++++++++++++++++++++++++++++++++ > doc/guides/linux_gsg/linux_drivers.rst | 10 +++ > lib/librte_eal/linux/eal_vfio.c | 93 +++++++++++----------------- > lib/librte_eal/linux/eal_vfio.h | 1 + > 6 files changed, 157 insertions(+), 58 deletions(-) > create mode 100644 app/test/test_vfio.c > > -- > 2.8.4 >
