linux-kernel - Re: [GIT PULL] x86/mm changes for v4.14: PCID support, 5-level paging support, Secure Memory Encryption support

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Date:   Tue, 5 Sep 2017 15:35:48 -0700
From:   Andy Lutomirski <luto@...nel.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Ingo Molnar <mingo@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andy Lutomirski <luto@...nel.org>,
        Borislav Petkov <bp@...en8.de>
Subject: Re: [GIT PULL] x86/mm changes for v4.14: PCID support, 5-level paging
 support, Secure Memory Encryption support

On Tue, Sep 5, 2017 at 3:33 PM, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
> On Tue, Sep 5, 2017 at 2:45 PM, Linus Torvalds
> <torvalds@...ux-foundation.org> wrote:
>>
>> I have bisected a bit deeper, and the pcid code is definitely in that
>> bisection window still. But are a fair number of other commits (about
>> 160 right now)
>
> Now down to 18.
>
> And one of those 18 is commit 10af6235e0d3 ("x86/mm: Implement PCID
> based optimization: try to preserve old TLB entries using PCID"),
> which I guess is where the problem might actually start showing up if
> it is pcid.
>
> I'll continue to bisect rather than just test "nopcid", because I want
> to get that bisection result regardless.

The thing that would surprise me about this is that I dogfooded my
PCID tree on my XPS 13 9250 for quite a while and it worked just fine.
Maybe something got merged oddly or had an unpleasant interaction
somewhere?

Anyway, all two cores of that fancy Skylake are compiling your tree as
we speak :).  It'll finish eventually.

--Andy