> On Thu, Sep 20, 2018 at 12:08:28PM -0700, Max Filippov wrote: > > I'm not familiar with the details of alloc_contig_range implementation, but > > I don't see how gfp_mask is used to limit allocation to non-high memory. > > So when alloc_contig_range gets start and end PFNs in high memory > > (from the CMA region allocated in high memory) it just returns high memory > > pages
Correct. alloc_contig_range doesn’t care where the PFNs are. The gpf_mask is completely ignored in this regard. > > -- that's what I see. On Fri, 21 Sep 2018 at 07:51, Christoph Hellwig <h...@lst.de> wrote: > I can't see what prevents people from doing a CMA in high memory either, That’s a feature. CMA can be configured such that different devices use different regions. One use case is separation of devices; another is devices with different address limits. > which is bad as except for arm non of the callers handles it completely > (and that includes xtensa, more below). > > CMA maintainers - is it intentional that CMA can be used to reserve and > return highmem pages? What Joonsoo said. I’ll just add that what you want to look at are invocations of dma_contiguous_reserve. For xtensa it’s: arch/xtensa/mm/init.c: dma_contiguous_reserve(PFN_PHYS(max_low_pfn)); which means that CMA’s default region will be placed below max_low_pfn. Undesired high memory CMA allocations on a given platform indicate that platform’s init code incorrectly places CMA region or the region is incorrectly configured in device tree. -- Best regards ミハウ “𝓶𝓲𝓷𝓪86” ナザレヴイツ «If at first you don’t succeed, give up skydiving» _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
