[Qemu-devel] Re: sparc32 do_unassigned_access overhaul

[Blue Swirl <blauwirbel@gmail.com>]

On Fri, Jan 15, 2010 at 9:11 PM, Artyom Tarasenko
<atar4qemu@googlemail.com> wrote:
> 2010/1/15 Blue Swirl <blauwirbel@gmail.com>:
>> On Fri, Jan 15, 2010 at 6:46 PM, Artyom Tarasenko
>> <atar4qemu@googlemail.com> wrote:
>>> According to pages 9-31 - 9-34 of "SuperSPARC & MultiCache Controller
>>> User's Manual":
>>>
>>> 1. "A lower priority fault may not overwrite the
>>>    MFSR status of a higher priority fault."
>>> 2. The MFAR is overwritten according to the policy defined for the MFSR
>>> 3. The overwrite bit is asserted if the fault status register (MFSR)
>>>   has been written more than once by faults of the same class
>>> 4. SuperSPARC will never place instruction fault addresses in the MFAR.
>>>
>>> Implementation of points 1-3 allows booting Solaris 2.6 and 2.5.1.
>>
>> Nice work! This also passes my tests.
>
> I'm afraid we still are not there yet though: Solaris 7 fails potentially due to
> another bug in the MMU emulation, and the initial [missing-] RAM
> detection in OBP fails
> very probably due to a bug in in the MMU emulation.

Some guesses:
 - Access to unassigned RAM area may be handled by the memory
controller differently (no faults, different faults etc.) than
unassigned access to SBus or other area.
 - Real RAM banks have aliasing effects (which could be emulated by
mapping the aliased RAM areas many times).
 - OBP on machines with ECC controller may detect missing RAM using ECC checks.

>> However, there are some CODING_STYLE issues.
>
> Is it something you do by hand (or, actually, by eyes), or is there a
> way I can automatically test my patches before sending?

There is CODING_STYLE document in the QEMU tree, please read it.

It's too bad we don't have a checkpatch script like Linux kernel has.
IIRC Anthony once said that he may write one.