On Fri 06-12-19 14:16:10, Thomas Hellstrom wrote: > 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? Yes. You can keep whatever is specific to TTM here but the rest should be somewhere visible to users of the interface and a note at vm_page_prot should help anybody touching the generic/core code to not break those expectations. Thanks! -- Michal Hocko SUSE Labs _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
