From mboxrd@z Thu Jan  1 00:00:00 1970
From: arnd@arndb.de (Arnd Bergmann)
Date: Wed, 30 Mar 2016 00:32:42 +0200
Subject: arm64: kernel v4.6-rc1 hangs on QEMU
In-Reply-To: <20160329222217.GA31869@yury-N73SV>
References: <20160329220502.GA14443@yury-N73SV> <3753214.GGjb33ZPlQ@wuerfel>
 <20160329222217.GA31869@yury-N73SV>
Message-ID: <3334343.7r57EH3qRj@wuerfel>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

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