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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Message-ID: <20170907080709.hwospdejr2ztmqr7@gmail.com>
Date:   Thu, 7 Sep 2017 10:07:09 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     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

* Linus Torvalds <torvalds@...ux-foundation.org> wrote:

> On Tue, Sep 5, 2017 at 2:40 PM, Ingo Molnar <mingo@...nel.org> wrote:
> >
> > Hm, just as background, there are no regression reports I'm aware of
> > against any of these trees, plus most of the dangerous commits have
> > been in linux-next for at least two weeks - the majority of them even
> > longer. The last 2-4 commits of x86/mm are fresher.
> 
> Side note: I do not believe a lot of people actually run linux-next on
> laptops, so suspend/resume likely doesn't get a lot of testing in
> next.
> 
> I think most people who run linux-next tend to be automation things on farms.

Yeah, so 10af6235e0d3 was in linux-next for over a month, yet no-one reported the 
bug.

> Don't get me wrong - I love linux-next and your tip testing, but I
> think linux-next is best for finding build errors etc big integration
> issues, with some very rudimentary actual boot checking.
> 
> Maybe I'm wrong.

I don't think you are wrong - most boot tests don't involve laptops. linux-next is 
mostly server oriented - and servers are often more debuggable than laptops. (Have 
actual serial ports or physical network connections with serial emulation, etc.)

I tried to maintain a laptop testbox in -tip testing with netconsole for a time - 
but it was quite a bit of pain so I eventually dropped it. (Not that the simple 
boot + kernel build test that -tip does would have uncovered this particular bug.)

Maybe a tester or two saw the 'dead on resume' bug and didn't bother reporting it, 
because it's a very difficult category of bug to debug short of a full bisection?

Thanks,

	Ingo