Re: SEV guest regression in 4.18

From: Sean Christopherson
Date: Wed Aug 22 2018 - 11:00:36 EST

On Wed, Aug 22, 2018 at 10:14:17AM +0200, Borislav Petkov wrote:
> Dropping Pavel as it bounces.
> On Tue, Aug 21, 2018 at 11:07:38AM -0500, Brijesh Singh wrote:
> > The tsc_early_init() is called before setup_arch() -> init_mem_mapping.
> Ok, I see it, thanks for explaining.
> So back to your original ideas - I'm wondering whether we should define
> a chunk of memory which the hypervisor and guest can share and thus
> communicate over... Something ala SEV-ES also with strictly defined
> layout and put all those variables there. And then the guest can map
> decrypted.

What about creating a data section specifically for shared memory?
The section would be PMD aligned and sized so that it could be mapped
appropriately without having to fracture the page. Then define a
macro to easily declare data in the new section, a la __read_mostly.

> There might be something similar though, I dunno.
> Maybe Paolo has a better idea...
> --
> Regards/Gruss,
> Boris.
> SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
> --