linux-kernel - Re: [PATCH 23/43] x86/mm/kaiser: Introduce user-mapped per-cpu areas

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Date:   Mon, 27 Nov 2017 13:14:57 -0800
From:   Dave Hansen <dave.hansen@...ux.intel.com>
To:     Borislav Petkov <bp@...en8.de>, Ingo Molnar <mingo@...nel.org>
Cc:     linux-kernel@...r.kernel.org,
        Andy Lutomirski <luto@...capital.net>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H . Peter Anvin" <hpa@...or.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH 23/43] x86/mm/kaiser: Introduce user-mapped per-cpu areas

On 11/26/2017 09:41 AM, Borislav Petkov wrote:
>> The KAISER approach keeps two copies of the page tables: one for running
>> in the kernel and one for running userspace.  But, there are a few
>> structures that are needed for switching in and out of the kernel and
>> a good subset of *those* are per-cpu data.
>>
>> This patch creates a new kind of per-cpu data that is mapped and
> Never say "This patch" in the commit message of a patch. It is
> tautologically useless.

Look at any academic paper's abstract.  They almost always describe the
problem and the state of the art, and then start to describe the paper's
content.  It's entirely normal to say "this paper" to help differentiate
these things.

Patches can and should be the same.

We should not litter the text with "this patch does this", "this patch
does that", but we should not outlaw it entirely.  IOW, you can't just
blindly say, not to do it.