linux-kernel - Re: [RFC Part1 PATCH 07/13] x86/compressed: register GHCB memory when SNP is active

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Message-ID: <20210408081740.GA10192@zn.tnic>
Date:   Thu, 8 Apr 2021 10:17:40 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Brijesh Singh <brijesh.singh@....com>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org, kvm@...r.kernel.org,
        ak@...ux.intel.com, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Joerg Roedel <jroedel@...e.de>,
        "H. Peter Anvin" <hpa@...or.com>, Tony Luck <tony.luck@...el.com>,
        Dave Hansen <dave.hansen@...el.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        David Rientjes <rientjes@...gle.com>,
        Sean Christopherson <seanjc@...gle.com>
Subject: Re: [RFC Part1 PATCH 07/13] x86/compressed: register GHCB memory
 when SNP is active

On Wed, Apr 07, 2021 at 12:34:59PM -0500, Brijesh Singh wrote:
> The feature is part of the GHCB version 2 and is enforced by the
> hypervisor. I guess it can be extended for the ES. Since this feature
> was not available in GHCB version 1 (base ES) so it should be presented
> as an optional for the ES ?

Yeah, it probably is not worth the effort. If an attacker controls the
guest kernel, then it can re-register a new GHCB so it doesn't really
matter.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette