Re: [Qemu-devel] [PATCH] spapr-pci: remove io ports workaround

[Alexey Kardashevskiy <aik@ozlabs.ru>]

On 01/03/2014 08:04 AM, Alexander Graf wrote:
> 
> On 11.12.2013, at 07:47, Alexey Kardashevskiy <aik@ozlabs.ru> wrote:
> 
>> On 12/10/2013 06:47 PM, Greg Kurz wrote:
>>> On Tue, 10 Dec 2013 13:43:05 +1100
>>> Alexey Kardashevskiy <aik@ozlabs.ru> wrote:
>>>> On 12/10/2013 03:33 AM, Greg Kurz wrote:
>>>>> In the past, IO space could not be mapped into the memory address space
>>>>> so we introduced a workaround for that. Nowadays it does not look
>>>>> necessary so we can remove the workaround and make sPAPR PCI
>>>>> configuration simplier.
>>>>>
>>>>> This workaround has also an evil side effect with virtio devices:
>>>>> because all PHBs have their .io region at the same address, the devices
>>>>> get mapped in the .io-alias region of every PHB (AKA. mapped multiple
>>>>> times). This breaks the ioeventfd feature and causes qemu to abort()
>>>>> when running with KVM and asking for more than one PHB:
>>>>>
>>>>> $ qemu-system-ppc64 -machine type=pseries,accel=kvm -smp 1 -m 4G \
>>>>>  -hda /local/greg/images/fedora-be.qcow2 \
>>>>>  -device
>>>>> virtio-9p-pci,fsdev=fsdev0,mount_tag=share,bus=pci,ioeventfd=on \
>>>>> -fsdev local,security_model=none,id=fsdev0,path=$HOME/share1 \ -device
>>>>> spapr-pci-host-bridge,index=15 kvm_mem_ioeventfd_add: error adding
>>>>> ioeventfd: File exists Aborted
>>>>>
>>>>> This will prevent to use virtio and VFIO passthrough at the same time,
>>>>> since VFIO needs a dedicated PHB to work on ppc.
>>>>>
>>>>> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
>>>>
>>>>
>>>> I have not seen this version yet so please remove me from "SOB". The patch
>>>> you replied to was eventually reworked and went to upstream as
>>>> 66aab867cedd2a2d81b4d64eff7c3e0f6f272bbf
>>>>
>>>
>>> Hi Alex,
>>>
>>> I agree you have not seen this version yet... The patch I replied to was my
>>> primary source of inspiration and contains these bits, hence the SOB. 
>>> Anyway, the SOB is now removed until you decide to add one yourself. :)
>>>
>>>> This one might be correct too but I want to try this first :)
>>>>
>>>
>>> Well, I hope it is. Please try it.
>>
>>
>> Yep. Tried. Looks good, did not break a thing as far as I can tell, even
>> VGA works :)
>>
>>
>> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
> 
> Thanks, applied to ppc-next.


Please read the rest of this thread. It does not visibly break things but
with this patch QEMU starts calling unassigned_mem_accepts() (normally
silent) which is not a good sign.



-- 
Alexey