linux-kernel - Re: [PATCH, RFC 00/62] Intel MKTME enabling

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Message-ID: <20190614121514.GK3436@hirez.programming.kicks-ass.net>
Date:   Fri, 14 Jun 2019 14:15:14 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc:     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>,
        Andy Lutomirski <luto@...capital.net>,
        David Howells <dhowells@...hat.com>,
        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 00/62] Intel MKTME enabling

On Wed, May 08, 2019 at 05:43:20PM +0300, Kirill A. Shutemov wrote:
> = Intro =
> 
> The patchset brings enabling of Intel Multi-Key Total Memory Encryption.
> It consists of changes into multiple subsystems:
> 
>  * Core MM: infrastructure for allocation pages, dealing with encrypted VMAs
>    and providing API setup encrypted mappings.

That wasn't eye-bleeding bad. With exception of the refcounting; that
looks like something that can easily go funny without people noticing.

>  * arch/x86: feature enumeration, program keys into hardware, setup
>    page table entries for encrypted pages and more.

That seemed incomplete (pageattr seems to be a giant hole).

>  * Key management service: setup and management of encryption keys.
>  * DMA/IOMMU: dealing with encrypted memory on IO side.

Just minor nits, someone else would have to look at this.

>  * KVM: interaction with virtualization side.

You really want to limit the damage random modules can do. They have no
business writing to the mktme variables.

>  * Documentation: description of APIs and usage examples.

Didn't bother with those; if the Changelogs are inadequate to make sense
of the patches documentation isn't the right place to fix things.

> The patchset is huge. This submission aims to give view to the full picture and
> get feedback on the overall design. The patchset will be split into more
> digestible pieces later.
> 
> Please review. Any feedback is welcome.

I still can't tell if this is worth the complexity :-/

Yes, there's a lot of words, but it doesn't mean anything to me, that
is, nothing here makes me want to build my kernel with this 'feature'
enabled.