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 10:58:41 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     Mike Galbraith <efault@....de>
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


* 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.

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