linux-kernel - Re: [PATCH, RFC 57/62] x86/mktme: Overview of Multi-Key Total Memory Encryption

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Date:   Sun, 14 Jul 2019 11:16:49 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Andrew Morton <akpm@...ux-foundation.org>, x86@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...en8.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...capital.net>,
        David Howells <dhowells@...hat.com>
Cc:     Kees Cook <keescook@...omium.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Kai Huang <kai.huang@...ux.intel.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        Alison Schofield <alison.schofield@...el.com>,
        linux-mm@...ck.org, kvm@...r.kernel.org, keyrings@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH, RFC 57/62] x86/mktme: Overview of Multi-Key Total Memory
 Encryption

On 5/8/19 7:44 AM, Kirill A. Shutemov wrote:
> From: Alison Schofield <alison.schofield@...el.com>
> 
> Provide an overview of MKTME on Intel Platforms.
> 
> Signed-off-by: Alison Schofield <alison.schofield@...el.com>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> ---
>  Documentation/x86/mktme/index.rst          |  8 +++
>  Documentation/x86/mktme/mktme_overview.rst | 57 ++++++++++++++++++++++
>  2 files changed, 65 insertions(+)
>  create mode 100644 Documentation/x86/mktme/index.rst
>  create mode 100644 Documentation/x86/mktme/mktme_overview.rst


> diff --git a/Documentation/x86/mktme/mktme_overview.rst b/Documentation/x86/mktme/mktme_overview.rst
> new file mode 100644
> index 000000000000..59c023965554
> --- /dev/null
> +++ b/Documentation/x86/mktme/mktme_overview.rst
> @@ -0,0 +1,57 @@
> +Overview
> +=========
...
> +--
> +1. https://software.intel.com/sites/default/files/managed/a5/16/Multi-Key-Total-Memory-Encryption-Spec.pdf
> +2. The MKTME architecture supports up to 16 bits of KeyIDs, so a
> +   maximum of 65535 keys on top of the “TME key” at KeyID-0.  The
> +   first implementation is expected to support 5 bits, making 63

Hi,
How do 5 bits make 63 keys available?

> +   keys available to applications.  However, this is not guaranteed.
> +   The number of available keys could be reduced if, for instance,
> +   additional physical address space is desired over additional
> +   KeyIDs.


thanks.
-- 
~Randy