Re: [Qemu-devel] [PATCH 5/7] PPC: Implement e500 (FSL) MMU

[Alexander Graf]

On 09.05.2011, at 21:27, Scott Wood wrote:

> On Sat, 7 May 2011 23:36:29 +0200
> Alexander Graf <address@hidden> wrote:
> 
>> On 07.05.2011, at 00:25, Scott Wood wrote:
>>>> +void helper_booke206_tlbsx(target_ulong address_hi, target_ulong 
>>>> address_lo)
>>> 
>>> What is address_hi?
>>> 
>>> From gen_tlbsx_booke206() it looks like these two arguments correspond to
>>> the two operands, so shouldn't they be added together?  I only see
>>> address_lo used.
>> 
>> Yup. According to the e500 spec:
>> 
>>  Note that rA = 0 is the preferred form for tlbsx and that some Freescale 
>> implementations, such as the e500, take an illegal instruction exception 
>> program interrupt if rA!=0.
>> 
>> So I figured that we're architecturally close enough if we just ignore it 
>> for now :).
> 
> Architecturally, ignoring it and taking a trap are significantly
> different. :-)
> 
> In practice it won't matter much, but it seems simple to handle it (why
> handle it in tlbivax but not here?), especially if this is to be general
> book3e code rather than e500.  I'm still confused about the "address_hi/lo"
> naming.

So what would you prefer? Just do whatever the 2.06 spec says and ignore e500 
specifics? :) Or always do what the e500 spec says?


Alex