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Re: [Qemu-ppc] [Qemu-devel] [PATCH 56/72] PPC: e500: Use new MPIC dt for
From: |
Alexander Graf |
Subject: |
Re: [Qemu-ppc] [Qemu-devel] [PATCH 56/72] PPC: e500: Use new MPIC dt format |
Date: |
Thu, 9 Aug 2012 23:01:36 +0200 |
On 09.08.2012, at 22:58, Scott Wood wrote:
> On 08/09/2012 03:52 PM, Alexander Graf wrote:
>>
>> On 09.08.2012, at 22:50, Scott Wood wrote:
>>
>>> 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 <address@hidden>
>>>>>>> Signed-off-by: Alexander Graf <address@hidden>
>>>>>>
>>>>>> 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.
>>
>> So I suppose the best would be to revert the whole patch and simply
>> go back to the old format then, to make sure we don't introduce more
>> oddness for non-Linux guests (not that I'm aware we're capable of
>> running any, especially any that would use the dtb).
>>
>> Once we have working large vectors in our MPIC emulation, we can
>> easily put the patch into place again and generate dt's that show an
>> fsl mpic.
>
> Additionally, we should consider adding extra compatibles with the major
> QEMU version in them, so that QEMU-aware target code can work around
> QEMU limitations even if it's been fixed in a more recent QEMU.
>
> I think this is what you were getting at in the e500 platform
> discussion, when you pointed at the PC versioning, but it's not about
> documenting semantics so much as identifying the actual implementation.
Yes, -M e500-1.2 should expose chrp,open-pic while -M e500 should expose
fsl,mpic. We also need to make the MPIC code capabilities conditional here, so
that large vectors are only supported when the machine requests them.
Alex
- Re: [Qemu-ppc] [PATCH 56/72] PPC: e500: Use new MPIC dt format, Alexander Graf, 2012/08/08
- Re: [Qemu-ppc] [PATCH 56/72] PPC: e500: Use new MPIC dt format, Scott Wood, 2012/08/08
- Re: [Qemu-ppc] [PATCH 56/72] PPC: e500: Use new MPIC dt format, Alexander Graf, 2012/08/09
- Re: [Qemu-ppc] [Qemu-devel] [PATCH 56/72] PPC: e500: Use new MPIC dt format, Scott Wood, 2012/08/09
- Re: [Qemu-ppc] [Qemu-devel] [PATCH 56/72] PPC: e500: Use new MPIC dt format, Alexander Graf, 2012/08/09
- Re: [Qemu-ppc] [Qemu-devel] [PATCH 56/72] PPC: e500: Use new MPIC dt format, Scott Wood, 2012/08/09
- Re: [Qemu-ppc] [Qemu-devel] [PATCH 56/72] PPC: e500: Use new MPIC dt format,
Alexander Graf <=
- Re: [Qemu-ppc] [Qemu-devel] [PATCH 56/72] PPC: e500: Use new MPIC dt format, Scott Wood, 2012/08/09
- Re: [Qemu-ppc] [Qemu-devel] [PATCH 56/72] PPC: e500: Use new MPIC dt format, Alexander Graf, 2012/08/09
- Re: [Qemu-ppc] [Qemu-devel] [PATCH 56/72] PPC: e500: Use new MPIC dt format, Scott Wood, 2012/08/09
- Re: [Qemu-ppc] [Qemu-devel] [PATCH 56/72] PPC: e500: Use new MPIC dt format, Alexander Graf, 2012/08/09
- Re: [Qemu-ppc] [Qemu-devel] [PATCH 56/72] PPC: e500: Use new MPIC dt format, Scott Wood, 2012/08/09
- Re: [Qemu-ppc] [Qemu-devel] [PATCH 56/72] PPC: e500: Use new MPIC dt format, Alexander Graf, 2012/08/09