linux-kernel - Re: SEV guest regression in 4.18

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Date:   Sat, 25 Aug 2018 06:47:49 +0200
From:   Borislav Petkov <bp@...e.de>
To:     Brijesh Singh <brijesh.singh@....com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "Lendacky, Thomas" <Thomas.Lendacky@....com>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: SEV guest regression in 4.18

On Fri, Aug 24, 2018 at 01:47:10PM -0500, Brijesh Singh wrote:
> I am more inclined towards creating a new section with PMD aligned and
> sized. This section will contains the decrypted data. In early
> boot code we will update the mapping with C=0. If caller wants to create
> a shared variable then it can do so with:
> 
> static int foo __decrypted;

Right, and keeping the SEV-ES's GHCB in mind, you could make that
section extensible so that the GHCB's 4K page can land there too. Maybe
something like a PMD-aligned range of 4K pages which are fully defined
and which hypervisor and guest can share and can be used for all kinds of
communication in the future...

-- 
Regards/Gruss,
    Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
--