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Date: Sat, 8 Jul 2017 11:24:26 +0200
From: Ingo Molnar <mingo@kernel.org>
To: Tom Lendacky <thomas.lendacky@amd.com>
Cc: linux-arch@vger.kernel.org, linux-efi@vger.kernel.org,
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Subject: Re: [PATCH v9 00/38] x86: Secure Memory Encryption (AMD)
Message-ID: <20170708092426.prf7xmmnv6xvdqx4@gmail.com>
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* Tom Lendacky <thomas.lendacky@amd.com> wrote:

> This patch series provides support for AMD's new Secure Memory Encryption (SME)
> feature.

I'm wondering, what's the typical performance hit to DRAM access latency when SME 
is enabled?

On that same note, if the performance hit is noticeable I'd expect SME to not be 
enabled in native kernels typically - but still it looks like a useful hardware 
feature. Since it's controlled at the page table level, have you considered 
allowing SME-activated vmas via mmap(), even on kernels that are otherwise not 
using encrypted DRAM?

One would think that putting encryption keys into such encrypted RAM regions would 
generally improve robustness against various physical space attacks that want to 
extract keys but don't have full control of the CPU.

Thanks,

	Ingo