Hi Michal, On Fri, 2019-12-06 at 11:30 +0100, Michal Hocko wrote: > 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! > Just to make sure I understand correctly. You'd prefer this (or similar) text to be present at the vmf_insert_mixed_prot() and vmf_insert_pfn_prot() definitions for MIXEDMAP and PFNMAP respectively, and a pointer from vm_page_prot to that text. Is that correct? Thanks, Thomas
