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

[Scott Wood <scottwood@freescale.com>]

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.

-Scott