Re: [Qemu-devel] [PATCH] ppc64: set MSR_SF bit

[Alexander Graf]

On 16.03.16 11:32, Thomas Huth wrote:
> 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 

 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 :).
> 
> Both, SLOF and OpenBIOS, seem to enable the SF bit manually, too, see:
> 
> https://github.com/qemu/openbios/blob/master/arch/ppc/qemu/start.S#L524
> 
> https://github.com/aik/SLOF/blob/master/board-qemu/llfw/startup.S#L91

Power up is slightly tricky, as machine state is pushed into the CPU
from the outside FWIW. I think we're "cleanest" if we just consider
power up a reset.

Reset is properly defined as an exception (0x100). For exceptions, the
970MP user manual for example says:

4.5 Exception Definitions
When an exception/interrupt is taken, all bits in the MSR are set to
‘0’, with the following exceptions:
• Exceptions always set MSR[SF] to ‘1’.


So the qemu fix is the correct one IMHO.

Alex

Re: [Qemu-devel] [PATCH] ppc64: set MSR_SF bit

[Thomas Huth]

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 
>>>
>>> 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 :).

Both, SLOF and OpenBIOS, seem to enable the SF bit manually, too, see:

https://github.com/qemu/openbios/blob/master/arch/ppc/qemu/start.S#L524

https://github.com/aik/SLOF/blob/master/board-qemu/llfw/startup.S#L91

 Thomas

Re: [Qemu-devel] [PATCH] ppc64: set MSR_SF bit

[Laurent Vivier]

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 
>>>
>>> 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
sldir12,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

Re: [Qemu-devel] [PATCH] ppc64: set MSR_SF bit

[Alexander Graf]

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 
>>
>> 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 :).


Alex

Re: [Qemu-devel] [PATCH] ppc64: set MSR_SF bit

[Laurent Vivier]

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 
> 
> 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

> Reviewed-by: Alexander Graf 

Thanks,
Laurent

>> ---
>>  target-ppc/translate_init.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/target-ppc/translate_init.c b/target-ppc/translate_init.c
>> index bd0cffc..d7a1aeb 100644
>> --- a/target-ppc/translate_init.c
>> +++ b/target-ppc/translate_init.c
>> @@ -9663,7 +9663,7 @@ static void ppc_cpu_reset(CPUState *s)
>>  
>>  #if defined(TARGET_PPC64)
>>  if (env->mmu_model & POWERPC_MMU_64) {
>> -env->msr |= (1ULL << MSR_SF);
>> +msr |= (1ULL << MSR_SF);
>>  }
>>  #endif
>>  
>>

Re: [Qemu-devel] [PATCH] ppc64: set MSR_SF bit

[Alexander Graf]

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 

I guess commit 2cf3eb6df552cee74b52de9989e270b74e42847e broke this. I'm
surprised it didn't cause us more problems :).

Reviewed-by: Alexander Graf 

> ---
>  target-ppc/translate_init.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/target-ppc/translate_init.c b/target-ppc/translate_init.c
> index bd0cffc..d7a1aeb 100644
> --- a/target-ppc/translate_init.c
> +++ b/target-ppc/translate_init.c
> @@ -9663,7 +9663,7 @@ static void ppc_cpu_reset(CPUState *s)
>  
>  #if defined(TARGET_PPC64)
>  if (env->mmu_model & POWERPC_MMU_64) {
> -env->msr |= (1ULL << MSR_SF);
> +msr |= (1ULL << MSR_SF);
>  }
>  #endif
>  
>