Re: [RFC PATCH v3 13/20] x86: DMA support for memory encryption

From	"Michael S. Tsirkin" <mst@redhat.com>
Newsgroups	linux.kernel
Subject	Re: [RFC PATCH v3 13/20] x86: DMA support for memory encryption
Date	2016-11-22 21:50 +0100
Message-ID	<sGqaR-3JU-3@gated-at.bofh.it> (permalink)
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On Tue, Nov 22, 2016 at 04:41:37PM +0100, Borislav Petkov wrote:
> 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?

Or even modify them. Guests generally trust devices since they
assume they are under their control.

> > 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.

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Re: [RFC PATCH v3 13/20] x86: DMA support for memory encryption "Michael S. Tsirkin" <mst@redhat.com> - 2016-11-15 16:20 +0100
  Re: [RFC PATCH v3 13/20] x86: DMA support for memory encryption "Michael S. Tsirkin" <mst@redhat.com> - 2016-11-15 20:20 +0100
  Re: [RFC PATCH v3 13/20] x86: DMA support for memory encryption Borislav Petkov <bp@alien8.de> - 2016-11-22 12:40 +0100
    Re: [RFC PATCH v3 13/20] x86: DMA support for memory encryption "Michael S. Tsirkin" <mst@redhat.com> - 2016-11-22 16:30 +0100
      Re: [RFC PATCH v3 13/20] x86: DMA support for memory encryption Borislav Petkov <bp@alien8.de> - 2016-11-22 16:50 +0100
        Re: [RFC PATCH v3 13/20] x86: DMA support for memory encryption "Michael S. Tsirkin" <mst@redhat.com> - 2016-11-22 21:50 +0100

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