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

Thomas Hellström (VMware) thomas_os at shipmail.org
Wed Sep 4 10:37:45 UTC 2019

On 9/4/19 9:53 AM, Daniel Vetter wrote:
> On Wed, Sep 4, 2019 at 8:49 AM Thomas Hellström (VMware)
> <thomas_os at shipmail.org> 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?


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