From: Arnd Bergmann <arnd@arndb.de>
To: Yury Norov <ynorov@caviumnetworks.com>
Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        alexey.klimov@linaro.org
Subject: Re: arm64: kernel v4.6-rc1 hangs on QEMU
Date: Wed, 30 Mar 2016 00:32:42 +0200
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On Wednesday 30 March 2016 01:22:17 Yury Norov wrote:
> > 
> > Undefined instruction in cpuinfo_store_boot_cpu() could be related
> > to the SYS_ID_AA64MMFR2_EL1 access that was recently added.
> > 
> > What does the architecture say about reading unknown cpuid registers?
> > 
> >       Arnd
> 
> ThunderX has some unimplemented system registers. AFAIR, attempt to access it
> causes data abort.

Ok, if that is the case, maybe the read_cpuid() macro can be changed
so it contains a fixup for the trap? That should handle both data abort
and undefinstr.

	Arnd