Re: [PATCH v2 5/6] platform/x86: intel_tdx_attest: Add TDX Guest attestation interface driver

[Kuppuswamy, Sathyanarayanan]

Hi Dave,

On 7/8/21 5:38 PM, Andi Kleen wrote:
> > Expensive and permanently fractures the direct map.
> >
> > I'm struggling to figure out why the direct map is even touched here.
> I think Sathya did it this way because the TD interface requires a physical address.
> > Why not just use a vmalloc area mapping?  You really just need *a*
> > decrypted mapping to the page.  You don't need to make *every* mapping
> > to the page decrypted.
>
> Yes it would be possible to use vmap() on the page and only set the vmap encrypted by passing the 
> right flags directly.

Is it alright to have non coherent mappings? If yes, any documentation reference for it?

> That would avoid breaking up the direct mapping.

--
Sathyanarayanan Kuppuswamy
Linux Kernel Developer