Subject: Re: KAISER: kexec triggers a warning
To: Juerg Haefliger <juerg.haefliger@canonical.com>,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org
References: <03012d01-4d04-1d58-aa93-425f142f9292@canonical.com>
Cc: mingo@kernel.org, tglx@linutronix.de, peterz@infradead.org,
        hughd@google.com, luto@kernel.org
From: Dave Hansen <dave.hansen@linux.intel.com>
Message-ID: <84c7dd7d-5e01-627e-6f26-5c1e30a87683@linux.intel.com>
Date: Fri, 1 Dec 2017 07:31:36 -0800
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On 12/01/2017 05:52 AM, Juerg Haefliger wrote:
> Loading a kexec kernel using today's linux-tip master with KAISER=y
> triggers the following warning:
> 
> [   18.054017] ------------[ cut here ]------------
> [   18.054024] WARNING: CPU: 0 PID: 1183 at
> ./arch/x86/include/asm/pgtable_64.h:258 native_set_p4d+0x5f/0x80
> [   18.054025] Modules linked in: nls_utf8 isofs ppdev nls_iso8859_1
> kvm_intel kvm irqbypass input_leds serio_raw i2c_piix4 parport_pc
> parport qemu_fw_cfg mac_hid 9p fscache ib_iser rdma_cm iw_cm ib_cm

This is kexec is messing with PTEs that map the kernel, which is OK for
kexec to do.  The warning is harmless.

The only question is whether we want to preserve _some_ kind of warning
there, or just axe it entirely.