Re: [Qemu-devel] [PATCH] PPC: booke206: Check for min/max TLB entry size

[Alexander Graf <agraf@suse.de>]

On 01/23/2012 06:28 PM, Scott Wood wrote:
> On 01/20/2012 08:43 PM, Alexander Graf wrote:
>>
>> Am 20.01.2012 um 21:01 schrieb Scott Wood<scottwood@freescale.com>:
>>> I'm not sure what happens when you write
>>> an entry to TLB1 with an invalid TSIZE.
>> What it says, the ISA means it's implementation dependent. What e500mc actually implements is an different question. Which still needs to be answered.
> AFAIK it's not documented what e500mc does for invalid sizes in TLB1, so
> I think anything that complies with the architecture's statement of any
> supported size is OK.
>
>> However for now I think wde 're ok by not modeling every odd corner case.
> Sure.  I was just curious about the architectural statement.
>
>>>> +    /* XXX only applies for MAV 1.0 */
>>>> +    size_tlb = (tlb->mas1&  MAS1_TSIZE_MASK)>>  (MAS1_TSIZE_SHIFT + 1);
>>>> +    size_min = (tlbncfg&  TLBnCFG_MINSIZE)>>  TLBnCFG_MINSIZE_SHIFT;
>>>> +    size_max = (tlbncfg&  TLBnCFG_MAXSIZE)>>  TLBnCFG_MAXSIZE_SHIFT;
>>>> +    if ((size_tlb>  size_max) || (size_tlb<  size_min)) {
>>>> +        /* set to min size */
>>>> +        tlb->mas1&= ~MAS1_TSIZE_MASK;
>>>> +        tlb->mas1 |= size_min<<  (MAS1_TSIZE_SHIFT + 1);
>>>> +    }
>>> You could just implement a bitmap now, which will work for MAV 2.0 as well.
>>>
>>> Especially since we're using the MAV 2.0 definition of tsize already, so
>>> min/max isn't an accurate way to describe what we support.
>> Not sure I follow. In MAV 1.0 the size constraints are defined in TLBnCFG, while for MAV 2.0 they are defned in their own bitmap registers (TLBnPS)
>>
>> Would you like to have a function called that returns a bitmap of
>> supported sizes for the TLB depending on its MAV value based on
>> either TLBnCFG or TLBnPS? We could then check if that size value bit
>> is set.
> Yes, use a bitmap internally regardless of how the programming model
> says we convey the information to the target code.

Already done :).


Alex