Re: [Qemu-devel] [Qemu-ppc] [PATCH 56/72] PPC: e500: Use new MPIC dt format

[Scott Wood <scottwood@freescale.com>]

On 08/09/2012 03:48 PM, Alexander Graf wrote:
> 
> On 09.08.2012, at 00:40, Scott Wood wrote:
> 
>> On 08/08/2012 04:16 PM, Alexander Graf wrote:
>>>
>>> On 24.06.2012, at 01:07, Alexander Graf wrote:
>>>
>>>> Due to popular demand, we're updating the way we generate the MPIC
>>>> node and interrupt lines based on what the current state of art is.
>>>>
>>>> Requested-by: Scott Wood <scottwood@freescale.com>
>>>> Signed-off-by: Alexander Graf <agraf@suse.de>
>>>
>>> Hey Scott,
>>>
>>> This patch breaks SMP for me. The reason for the breakage is that
>>> Linux does some things differently when it finds an fsl,mpic instead
>>> of a generic openpic. I have assembled logs between a working version
>>> (compatible openpic) and a broken version (compatible fsl,mpic) with
>>> guest and host debug turned on.
>>>
>>> Maybe you have an idea what's going wrong.
>>
>> IIRC QEMU is missing support for large vectors, which is probably
>> breaking IPIs.  A recent change to Linux has it assuming it can use
>> large vectors when it sees fsl,mpic, as we're running out of vectors (on
>> p4080 MSIs collided with the arbitrarily chosen timer vector, and on
>> t4240 the normal internal interrupts alone go beyond 256).
>>
>> We need to get the enhancements from our internal KVM MPIC back into QEMU.
> 
> Ok, so the quick fix for 1.2 would be to revert to the old compatible
> name. Can we leave the 4-field interrupt numbers or do we need to
> revert the whole patch?

In theory you shouldn't have 4-cell interrupt numbers without fsl,mpic,
but I don't think it will actually break in Linux -- the extra cells
should just be ignored.

-Scott