Date: Tue, 22 Nov 2016 16:41:37 +0100
From: Borislav Petkov <bp@alien8.de>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>, linux-arch@vger.kernel.org,
        linux-efi@vger.kernel.org, kvm@vger.kernel.org,
        linux-doc@vger.kernel.org, x86@kernel.org,
        linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com,
        linux-mm@kvack.org, iommu@lists.linux-foundation.org,
        Rik van Riel <riel@redhat.com>,
        Radim =?utf-8?B?S3LEjW3DocWZ?= <rkrcmar@redhat.com>,
        Arnd Bergmann <arnd@arndb.de>, Jonathan Corbet <corbet@lwn.net>,
        Matt Fleming <matt@codeblueprint.co.uk>,
        Joerg Roedel <joro@8bytes.org>,
        Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Larry Woodman <lwoodman@redhat.com>, Ingo Molnar <mingo@redhat.com>,
        Andy Lutomirski <luto@kernel.org>, "H. Peter Anvin" <hpa@zytor.com>,
        Andrey Ryabinin <aryabinin@virtuozzo.com>,
        Alexander Potapenko <glider@google.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Dmitry Vyukov <dvyukov@google.com>
Subject: Re: [RFC PATCH v3 13/20] x86: DMA support for memory encryption
Message-ID: <20161122154137.z5vp3xcl5cpesuiz@pd.tnic>
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On Tue, Nov 22, 2016 at 05:22:38PM +0200, Michael S. Tsirkin wrote:
> The issue is it's a (potential) security hole, not a slowdown.

How? Because the bounce buffers will be unencrypted and someone might
intercept them?

> To disable unsecure things. If someone enables SEV one might have an
> expectation of security.  Might help push vendors to do the right thing
> as a side effect.

Ok, you're looking at the SEV-cloud-multiple-guests aspect. Right, that
makes sense.

I guess for SEV we should even flip the logic: disable such devices by
default and an opt-in option to enable them and issue a big fat warning.
I'd even want to let the guest users know that they're on a system which
cannot give them encrypted DMA to some devices...

-- 
Regards/Gruss,
    Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.