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From: Laurent Vivier <lvivier@redhat.com>
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Date: Wed, 16 Mar 2016 11:30:12 +0100
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Subject: Re: [Qemu-devel] [PATCH] ppc64: set MSR_SF bit
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To: Alexander Graf <agraf@suse.de>
Cc: dgibson@redhat.com, thuth@redhat.com, qemu-ppc@nongnu.org, qemu-devel@nongnu.org



On 16/03/2016 11:06, Alexander Graf wrote:
> 
> 
> On 16.03.16 11:05, Laurent Vivier wrote:
>> On 16/03/2016 10:48, Alexander Graf wrote:
>>>
>>>
>>> On 16.03.16 10:43, Laurent Vivier wrote:
>>>> When a qemu-system-ppc64 is started, the 64-bit mode bit
>>>> is not set in MSR.
>>>>
>>>> Signed-off-by: Laurent Vivier <lvivier@redhat.com>
>>>
>>> I guess commit 2cf3eb6df552cee74b52de9989e270b74e42847e broke this. I'm
>>> surprised it didn't cause us more problems :).
>>
>> Linux kernel is ready to manage that: see enable_64b_mode in
>> arch/powerpc/kernel/head_64.S
> 
> We don't boot Linux directly though, only openBIOS and SLOF :).

Same thing in SLOF:

./board-qemu/llfw/startup.S

_start:
...
        mfmsr   r11                     /* grab the current MSR */
        li      r12,(MSR_SF | MSR_ISF)@highest
        sldi    r12,r12,48
        or      r11,r11,r12
        mtmsrd  r11
        isync

And openbios seems to disable it explicitly:

./arch/ppc/qemu/start.S

_entry:
...
   /* clear MSR, disable MMU, SF */

[BTW, I've never been able to compile a 64bit version of openbios...]

Laurent