On Fri 06-12-19 09:24:26, Thomas Hellström (VMware) wrote: [...] > @@ -283,11 +282,26 @@ vm_fault_t ttm_bo_vm_fault_reserved(struct vm_fault *vmf, > pfn = page_to_pfn(page); > } > > + /* > + * Note that the value of @prot at this point may differ from > + * the value of @vma->vm_page_prot in the caching- and > + * encryption bits. This is because the exact location of the > + * data may not be known at mmap() time and may also change > + * at arbitrary times while the data is mmap'ed. > + * This is ok as long as @vma->vm_page_prot is not used by > + * the core vm to set caching- and encryption bits. > + * This is ensured by core vm using pte_modify() to modify > + * page table entry protection bits (that function preserves > + * old caching- and encryption bits), and the @fault > + * callback being the only function that creates new > + * page table entries. > + */ While this is a very valuable piece of information I believe we need to document this in the generic code where everybody will find it. vmf_insert_mixed_prot sounds like a good place to me. So being explicit about VM_MIXEDMAP. Also a reference from vm_page_prot to this function would be really helpeful. Thanks! -- Michal Hocko SUSE Labs
