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

[Alexander Graf]

On 02.01.2014, at 23:08, Alexey Kardashevskiy <address@hidden> wrote:

> On 01/03/2014 08:04 AM, Alexander Graf wrote:
>> 
>> On 11.12.2013, at 07:47, Alexey Kardashevskiy <address@hidden> wrote:
>> 
>>> On 12/10/2013 06:47 PM, Greg Kurz wrote:
>>>> On Tue, 10 Dec 2013 13:43:05 +1100
>>>> Alexey Kardashevskiy <address@hidden> 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 <address@hidden>
>>>>> 
>>>>> 
>>>>> 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 <address@hidden>
>> 
>> 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.

Oops, I thought your comment meant this was fixed. I took it off the queue 
again :).


Alex