linux-kernel - Re: v4.4-rc8 based tip tree kernel hangs on boot.

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Date:	Mon, 11 Jan 2016 16:10:30 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Matt Fleming <matt@...eblueprint.co.uk>
Cc:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	Ingo Molnar <mingo@...e.hu>,
	LKML <linux-kernel@...r.kernel.org>, linux-efi@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: v4.4-rc8 based tip tree kernel hangs on boot.


* Matt Fleming <matt@...eblueprint.co.uk> wrote:

> On Mon, 11 Jan, at 12:59:21AM, Srikar Dronamraju wrote:
> > On a x86_64 machine, I see kernel v4.4-rc8 based tip tree hangs on boot.
> > However v4.4-rc8 with the same config boots well on the same machine.
> > 
> > git bisect results are as follows
> > 
> > git bisect start
> > # bad: [fc4e8fa9f80e0f099838f3a9997019de36d9a4ba] Merge branch 'WIP.x86/mm'
> > git bisect bad fc4e8fa9f80e0f099838f3a9997019de36d9a4ba
> > # good: [168309855a7d1e16db751e9c647119fe2d2dc878] Linux 4.4-rc8
> > git bisect good 168309855a7d1e16db751e9c647119fe2d2dc878
> > # good: [76e17c25ebc9f6619f9f8fd93f3905b0def8dc6f] Merge branch 'perf/core'
> > git bisect good 76e17c25ebc9f6619f9f8fd93f3905b0def8dc6f
> > # good: [e8998ce7e8ce42419d0c7bb08c105bd860eb3218] Merge branch 'timers/urgent'
> > git bisect good e8998ce7e8ce42419d0c7bb08c105bd860eb3218
> > # good: [af51cdabdbea5355ed388b8b3a7cf9bfc0864b9c] Merge branch 'x86/cpu'
> > git bisect good af51cdabdbea5355ed388b8b3a7cf9bfc0864b9c
> > # bad: [5852b88267adcc78722fc5d4f45751fb6e261bd2] Merge branch 'x86/urgent'
> > git bisect bad 5852b88267adcc78722fc5d4f45751fb6e261bd2
> > # bad: [c236714fd39fb26993af2d5fde9c3bfc32361323] Merge branch 'x86/fpu'
> > git bisect bad c236714fd39fb26993af2d5fde9c3bfc32361323
> > # bad: [ff3d0a12fb2dc123e2b46e9524ebf4e08de5c59c] Documentation/x86: Update EFI memory region description
> > git bisect bad ff3d0a12fb2dc123e2b46e9524ebf4e08de5c59c
> > # bad: [b61a76f8850d2979550abc42d7e09154ebb8d785] x86/efi: Map RAM into the identity page table for mixed mode
> > git bisect bad b61a76f8850d2979550abc42d7e09154ebb8d785
> > # bad: [edc3b9129cecd0f0857112136f5b8b1bc1d45918] x86/mm/pat: Ensure cpa->pfn only contains page frame numbers
> > git bisect bad edc3b9129cecd0f0857112136f5b8b1bc1d45918
> > # bad: [21cdb6b568435738cc0b303b2b3b82742396310c] x86/mm: Page align the '_end' symbol to avoid pfn conversion bugs
> > git bisect bad 21cdb6b568435738cc0b303b2b3b82742396310c
> > # first bad commit: [21cdb6b568435738cc0b303b2b3b82742396310c] x86/mm: Page align the '_end' symbol to avoid pfn conversion bugs
> > 
> > Not much info on the console, when the kernel hangs.
>  
> What info is there?
> 
> > Tried reverting Commit 21cdb6b56 "x86/mm: Page align the '_end'
> > symbol to avoid pfn conversion bugs" but that doesnt help.
> 
> Odd. Could you try booting the tip/x86/efi branch instead? There's
> only a handful of patches on that branch so it should be pretty easy
> to narrow down the problematic change.

Yes, that would be nice, you can get it via:

  git checkout v4.4
  git pull git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git x86/efi

Meanwhile I'm holding off on sending the pending EFI bits to Linus, conditional on 
the outcome of this regression report.

Thanks,

	Ingo