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Subject: Re: 2f47e7e19f ("x86/mm/kaiser: Use PCID feature to make user and
 .."): WARNING: CPU: 0 PID: 1 at mm/early_ioremap.c:114 __early_ioremap
To: Ingo Molnar <mingo@kernel.org>,
        kernel test robot <fengguang.wu@intel.com>
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 <20171127101814.jsglrh7typy3pxxp@gmail.com>
Cc: LKP <lkp@01.org>, kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
        Thomas Gleixner <tglx@linutronix.de>, wfg@linux.intel.com
From: Dave Hansen <dave.hansen@linux.intel.com>
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Date: Mon, 27 Nov 2017 06:51:12 -0800
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On 11/27/2017 02:18 AM, Ingo Molnar wrote:
> Any ideas about this bug?

I suspect that it's not bisected perfectly.  I did some testing with
that config and it pretty much boots or crashes randomly.

Booting in a VM on a CPU without PCID support gets crashes in early
userspace, which has tended to be a TLB flushing problem.  I'll narrow
it down some more today.