Re: [Qemu-devel] [PATCH] target-ppc: set MSR_CM bit for BookE 2.06 MMU

[Michael Walle <michael@walle.cc>]

Am 2016-07-22 15:07, schrieb Alexander Graf:
>> On 22 Jul 2016, at 15:00, Michael Walle <michael@walle.cc> wrote:
>> 
>> 64 bit user mode doesn't work for the e5500 core because the MSR_CM 
>> bit is
>> not set which enables the 64 bit mode for this MMU model. Memory 
>> addresses
>> are truncated to 32 bit, which results in "Invalid data memory access"
>> error messages. Fix it by setting the MSR_CM bit for this MMU model.
>> 
>> Signed-off-by: Michael Walle <michael@walle.cc>
>> ---
>> target-ppc/translate_init.c | 3 +++
>> 1 file changed, 3 insertions(+)
>> 
>> diff --git a/target-ppc/translate_init.c b/target-ppc/translate_init.c
>> index 5ecafc7..1ebb143 100644
>> --- a/target-ppc/translate_init.c
>> +++ b/target-ppc/translate_init.c
>> @@ -10218,6 +10218,9 @@ static void ppc_cpu_reset(CPUState *s)
>>     if (env->mmu_model & POWERPC_MMU_64) {
>>         msr |= (1ULL << MSR_SF);
>>     }
>> +    if (env->mmu_model == POWERPC_MMU_BOOKE206) {
> 
> Is this check correct? Doesn’t e500mc adhere to 2.06 as well? Running
> 
>   qemu-system-ppc64 -M ppce500 -cpu e500mc …
> 
> is perfectly valid and should just work. With your patch, it would
> start in invalid 64bit mode :).
> 
> 
> Alex

Mhh, sorry I don't really have any understanding of the PPC state after 
reset. Should have flagged this as RFC.

Maybe I should explain my issue. I'm debugging a problem with the 64 bit 
linux-user variant (qemu-ppc64). There the first instructions causes an 
"Invalid data memory access" because the address is truncated to 32 bit. 
This is because the msr_is_64bit() returns false in my case. So first 
question here, is qemu-ppc64 supposed to set the MSR to 64bit mode? I 
guess so, because 32bit mode would be the qemu-ppc binary. What is the 
MSR state in full system emulation for a e5500 core? 64bit or 32bit?

If it is 32bit, the simple solution would be to put #ifdef 
CONFIG_USER_ONLY around my patch, right?
If the MMU is in 64bit mode after reset, I would have to check for the 
e5500, too. Mhh, I don't see that this information is available in 
ppc_cpu_reset().

-michael