linux-kernel - Re: [PATCH v3 5/5] x86/sev-es: Do not support MMIO to/from encrypted memory

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Date:   Tue, 27 Oct 2020 12:26:35 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Joerg Roedel <joro@...tes.org>
Cc:     x86@...nel.org, Joerg Roedel <jroedel@...e.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Kees Cook <keescook@...omium.org>,
        Arvind Sankar <nivedita@...m.mit.edu>,
        Martin Radev <martin.b.radev@...il.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 5/5] x86/sev-es: Do not support MMIO to/from encrypted
 memory

On Wed, Oct 21, 2020 at 02:39:38PM +0200, Joerg Roedel wrote:
> From: Joerg Roedel <jroedel@...e.de>
> 
> MMIO memory is usually not mapped encrypted, so there is no reason to
> support emulated MMIO when it is mapped encrypted.
> 
> This prevents a possible hypervisor attack where it maps a RAM page as

"Prevent... "

> an MMIO page in the nested page-table, so that any guest access to it
> will trigger a #VC exception and leak the data on that page to the
						^

"... via the GHCB (like with normal MMIO)... "

Thx.

-- 
Regards/Gruss,
    Boris.

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