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Subject: Re: [BUG] GPF on reboot of box
From: Nadav Amit <nadav.amit@gmail.com>
In-Reply-To: <20171006213956.0b33cf61@gandalf.local.home>
Date: Fri, 6 Oct 2017 19:21:26 -0700
Cc: LKML <linux-kernel@vger.kernel.org>, Andy Lutomirski <luto@kernel.org>,
        Boris Ostrovsky <boris.ostrovsky@oracle.com>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>
Message-Id: <90068838-FBC3-4492-9D50-293509574617@gmail.com>
References: <20171006213956.0b33cf61@gandalf.local.home>
To: Steven Rostedt <rostedt@goodmis.org>
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Steven Rostedt <rostedt@goodmis.org> wrote:

> Starting with v4.14-rc1 my box crashes during a reboot. All I get is
> the following:
> 
> [  250.615793] sd 0:0:0:0: [sda] Synchronizing SCSI cache
> [  250.635639] reboot: Restarting system
> [  250.639671] reboot: machine restart
> [  250.643842] general protection fault: 0000 [#1] PREEMPT SMP KASAN
> 
> Then nothing. No reboot, it just hangs there.
> 
> I bisected it down to this commit:
> 
> 660da7c9228f ("x86/mm: Enable CR4.PCIDE on supported systems")
> 
> If I comment out the setting of X86_CR4_PCIDE in that commit, it boots
> fine. But...
> 
> I noticed that commit c7ad5ad29 ("x86/mm/64: Initialize CR4.PCIDE
> early") moved the problem code from arch/x86/kernel/cpu/common.c to
> arch/x86/mm/init.c
> 
> If I comment it out in v4.14-rc1, it crashes on boot up.
> 
> It appears that my box doesn't like having X86_CR4_PCIDE set. it causes
> reboot to fail. But it also appears that setting that is required for
> some other code to work.

IIRC, there was a problem in rc1, which should be resolved in newer rcs.
If you need to run rc1, you can try to use the kernel parameter “nopcid".

Nadav