linux-kernel - Re: tip -ENOBOOT - bisected to locking/refcounts, x86/asm: Implement fast refcount overflow protection

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Date:   Tue, 29 Aug 2017 11:21:31 +0200
From:   Mike Galbraith <efault@....de>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     Kees Cook <keescook@...omium.org>,
        LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Thomas Gleixner <tglx@...utronix.de>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Elena Reshetova <elena.reshetova@...el.com>,
        Arnd Bergmann <arnd@...db.de>, "H. Peter Anvin" <hpa@...or.com>
Subject: Re: tip -ENOBOOT - bisected to locking/refcounts, x86/asm:
 Implement fast refcount overflow protection

On Tue, 2017-08-29 at 10:58 +0200, Ingo Molnar wrote:
> * Mike Galbraith <efault@....de> wrote:
> 
> > Greetings,
> > 
> > Take 2 of KVM bisect as you work fingered $subject.  Take 1 was stymied
> > by build dependencies (aa5d1b81, df340524) which I foolishly tried to
> > skip, leading git bisect to end up handing me a list of commits that
> > might be busted.  During take 2, I added those two as required.
> > 
> > Symptom is a few splats as below, with box finally hanging.  Network
> > comes up, but neither ssh nor console login is possible.
> 
> Just to double check, does the patch below also cure the regression?
> If we don't find the bug it might be safer than a full revert.

I reverted it, and vbox now boots.  Should I still try the below?

> 
> Thanks,
> 
> 	Ingo
> 
>  arch/x86/Kconfig | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index d04809921993..3b83ef8f1e9b 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -55,7 +55,7 @@ config X86
>  	select ARCH_HAS_KCOV			if X86_64
>  	select ARCH_HAS_MMIO_FLUSH
>  	select ARCH_HAS_PMEM_API		if X86_64
> -	select ARCH_HAS_REFCOUNT
> +#	select ARCH_HAS_REFCOUNT
>  	select ARCH_HAS_UACCESS_FLUSHCACHE	if X86_64
>  	select ARCH_HAS_SET_MEMORY
>  	select ARCH_HAS_SG_CHAIN