On Wed, Sep 4, 2019 at 12:38 PM Thomas Hellström (VMware) <thomas_os@xxxxxxxxxxxx> wrote: > > On 9/4/19 9:53 AM, Daniel Vetter wrote: > > On Wed, Sep 4, 2019 at 8:49 AM Thomas Hellström (VMware) > > <thomas_os@xxxxxxxxxxxx> wrote: > >> On 9/4/19 1:15 AM, Andy Lutomirski wrote: > >>> But, reading this, I have more questions: > >>> > >>> Can’t you get rid of cvma by using vmf_insert_pfn_prot()? > >> It looks like that, although there are comments in the code about > >> serious performance problems using VM_PFNMAP / vmf_insert_pfn() with > >> write-combining and PAT, so that would require some serious testing with > >> hardware I don't have. But I guess there is definitely room for > >> improvement here. Ideally we'd like to be able to change the > >> vma->vm_page_prot within fault(). But we can > > Just a quick comment on this: It's the repeated (per-pfn/pte) lookup > > of the PAT tables, which are dead slow. If you have a struct > > io_mapping then that can be done once, and then just blindly inserted. > > See remap_io_mapping in i915. > > -Daniel > > Thanks, Daniel. > > Indeed looks a lot like remap_pfn_range(), but usable at fault time? Yeah we call it from our fault handler. It's essentially vm_insert_pfn except the pat track isn't there, but instead relies on the pat tracking io_mapping has done already. -Daniel -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
