Re: [Qemu-devel] [PATCH 8/8] PPC: Add e5500 CPU target

[Scott Wood <scottwood@freescale.com>]

On 06/20/2012 06:10 PM, Alexander Graf wrote:
> 
> On 21.06.2012, at 01:07, Scott Wood wrote:
> 
>> On 06/20/2012 05:59 PM, Alexander Graf wrote:
>>>
>>> On 21.06.2012, at 00:26, Scott Wood wrote:
>>>
>>>> On 06/20/2012 03:11 PM, Alexander Graf wrote:
>>>>> +    /* XXX better abstract into Emb.xxx features */
>>>>> +    if (version == fsl_e5500) {
>>>>> +        spr_register(env, SPR_BOOKE_EPCR, "EPCR",
>>>>> +                     SPR_NOACCESS, SPR_NOACCESS,
>>>>> +                     &spr_read_generic, &spr_write_generic,
>>>>> +                     0x00000000);
>>>>> +        spr_register(env, SPR_BOOKE_MAS7_MAS3, "MAS7_MAS3",
>>>>> +                     SPR_NOACCESS, SPR_NOACCESS,
>>>>> +                     &spr_read_mas73, &spr_write_mas73,
>>>>> +                     0x00000000);
>>>>> +        env->reset_msr = (1ULL < MSR_CM);
>>>>
>>>> That's a funny way of writing "env->reset_msr = 0". :-)
>>>>
>>>> Assuming you really meant "env->reset_msr = 1ULL << MSR_CM", why?  We
>>>> enter the kernel in 32-bit mode.  It resets in 32-bit mode as well, if
>>>> we ever implement that for e5500 QEMU.
>>>
>>> Hrm. At least my self-compiled kernel did issue an "ld" instruction before going into MSR_CM mode, hence I figured we need it.
>>
>> You don't need MSR_CM to run 64-bit instructions.  It just affects
>> masking in certain places.
> 
> Wait - you don't? Is there a comprehensive description on what MSR_CM really does and does not?

Not that I know of -- you need to search the ISA for places that mention
MSR[CM] or 64-bit mode.

-Scott