iommu/vt-d: Calculate mask for non-aligned flushes
stable inclusion from stable-v5.10.115 commit 2e6f3d665a29fe15fffd155d35d13f8c4d119d38 category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I5IZ9C Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2e6f3d665a29fe15fffd155d35d13f8c4d119d38 -------------------------------- commit 59bf3557 upstream. Calculate the appropriate mask for non-size-aligned page selective invalidation. Since psi uses the mask value to mask out the lower order bits of the target address, properly flushing the iotlb requires using a mask value such that [pfn, pfn+pages) all lie within the flushed size-aligned region. This is not normally an issue because iova.c always allocates iovas that are aligned to their size. However, iovas which come from other sources (e.g. userspace via VFIO) may not be aligned. To properly flush the IOTLB, both the start and end pfns need to be equal after applying the mask. That means that the most efficient mask to use is the index of the lowest bit that is equal where all higher bits are also equal. For example, if pfn=0x17f and pages=3, then end_pfn=0x181, so the smallest mask we can use is 8. Any differences above the highest bit of pages are due to carrying, so by xnor'ing pfn and end_pfn and then masking out the lower order bits based on pages, we get 0xffffff00, where the first set bit is the mask we want to use. Fixes: 6fe1010d ("vfio/type1: DMA unmap chunking") Cc: stable@vger.kernel.org Signed-off-by:David Stevens <stevensd@chromium.org> Reviewed-by:
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