linux-kernel - Re: x86-tip.today (4cdf573) early instaboot

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Message-ID: <1523363877.4942.2.camel@gmx.de>
Date:   Tue, 10 Apr 2018 14:37:57 +0200
From:   Mike Galbraith <efault@....de>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     Ingo Molnar <mingo@...e.hu>, LKML <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Dave Hansen <dave.hansen@...ux.intel.com>
Subject: Re: x86-tip.today (4cdf573)  early instaboot

On Tue, 2018-04-10 at 10:59 +0200, Ingo Molnar wrote:
> * Mike Galbraith <efault@....de> wrote:
> 
> > Hi Ingo,
> > 
> > FYI, my i4790 box reboots immediately.. or close enough to it that you
> > see nothing at all before again meeting the bios splash.  Master with
> > the ~same config works fine.  I haven't poked around yet (work).
> 
> Hm, so there's been a few 'dangerous' pieces of work merged yesterday-ish.
> 
> Prime suspects would be:
> 
>  triton:~/tip> gll linus..x86/pti
> 
>  0564258fb2cf: x86/pti: Leave kernel text global for !PCID
>  a5df4f1f0d78: x86/pti: Never implicitly clear _PAGE_GLOBAL for kernel image
>  e0bb456e3250: x86/pti: Enable global pages for shared areas
>  efad2b415152: x86/mm: Do not forbid _PAGE_RW before init for __ro_after_init
>  4ddee6efdcd0: x86/mm: Comment _PAGE_GLOBAL mystery
>  e71e836f463d: x86/mm: Remove extra filtering in pageattr code
>  64c80759408f: x86/mm: Do not auto-massage page protections  <== WOOF
>  6baf4bec02db: x86/espfix: Document use of _PAGE_GLOBAL
>  8a57f4849f4f: x86/mm: Introduce "default" kernel PTE mask
>  606c7193d5fb: x86/mm: Undo double _PAGE_PSE clearing
>  d1440b23c922: x86/mm: Factor out pageattr _PAGE_GLOBAL setting
>  ee1400dda318: Merge branch 'linus' into x86/pti to pick up upstream changes
>  071ccc966ba5: x86/entry/64: Drop idtentry's manual stack switch for user entries
>  9820e1c3376c: x86/uapi: Fix asm/bootparam.h userspace compilation errors
> 
> ... which you could test via 0564258fb2cf: if that insta-reboots too then 
> 9820e1c3376c^1 is expected to work and 4 bisection steps should pinpoint the 
> guilty commit ...

Thanks.  I already had a full bisect running, so ended up doing more
than 4 steps, but ended up at the above.

	-Mike