linux-kernel - Re: [PATCH] powerpc/64s: Clear PCR on boot

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Message-ID: <31148B04-5AA9-4F4F-BD34-CD9665F7F6D6@ellerman.id.au>
Date:   Sun, 27 May 2018 12:22:23 +1000
From:   Michael Ellerman <michael@...erman.id.au>
To:     Guenter Roeck <linux@...ck-us.net>,
        Michael Neuling <mikey@...ling.org>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>
CC:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] powerpc/64s: Clear PCR on boot



On 25 May 2018 11:33:08 pm AEST, Guenter Roeck <linux@...ck-us.net> wrote:
>On Fri, May 18, 2018 at 11:37:42AM +1000, Michael Neuling wrote:
>> Clear the PCR (Processor Compatibility Register) on boot to ensure we
>> are not running in a compatibility mode.
>> 
>> We've seen this cause problems when a crash (and kdump) occurs while
>> running compat mode guests. The kdump kernel then runs with the PCR
>> set and causes problems. The symptom in the kdump kernel (also seen
>in
>> petitboot after fast-reboot) is early userspace programs taking
>> sigills on newer instructions (seen in libc).
>> 
>
>Hi folks,
>
>this patch causes qemu to bail out with
>
>Trying to write privileged spr 338 (0x152) at c000000000033454
>
>when running it with "-M powernv -cpu POWER8" and powernv_defconfig.
>
>Can you confirm that this is a bug in qemu ?

Hi Guenter,

Thanks for the report. As far as I'm concerned this is a qemu bug, that register should exist on a bare metal Power8.

Will try and get you a qemu patch to fix it.

cheers

-- 
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