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

[Guenter Roeck]

Hi Michael,

On Sun, May 27, 2018 at 12:22:23PM +1000, Michael Ellerman wrote:
> 
> 
> On 25 May 2018 11:33:08 pm AEST, Guenter Roeck <linux@xxxxxxxxxxxx> 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.
> 
I already have a patch, or at least one that does the trick for me.
Getting qemu patched was not the problem. I just want to be sure that
the problem is indeed a qemu problem.

Thanks,
Guenter

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