Re: [PATCH v2 3/4] drm/ttm, drm/vmwgfx: Correctly support support AMD memory encryption

[Thomas HellstrÃm (VMware)]

On 9/4/19 9:53 AM, Daniel Vetter wrote:
> On Wed, Sep 4, 2019 at 8:49 AM Thomas HellstrÃm (VMware)
> <thomas_os@xxxxxxxxxxxx> wrote:
> > On 9/4/19 1:15 AM, Andy Lutomirski wrote:
> > > But, reading this, I have more questions:
> > >
> > > Canât 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?

/Thomas