Re: [Qemu-devel] [Qemu-arm] [PATCH v4 0/5] virtio-iommu: VFIO integration

[Auger Eric <eric.auger@redhat.com>]

Hi Bharat,

On 06/10/2017 05:46, Bharat Bhushan wrote:
> 
> 
>>>> Thanks
>>>>
>>>> Eric
>>>>>
>>>>> However you should be allowed to map 1 sg element of 5 pages and
>>>>> then notify the host about this event I think. Still looking at the code...
>>>>>
>>>>> I still can't reproduce the issue at the moment. What kind of device
>>>>> are you assigning?
>>>>>
>>>>> Thanks
>>>>>
>>>>> Eric
>>>>>>
>>>>>> Atleast vfio_get_vaddr called from vfio_iommu_map_notify in Qemu
>>>>>> expects the map size to be a power of 2.
>>>
>>> Actually I missed the most important here ;-)
>>>>>>
>>>>>>  if (len & iotlb->addr_mask) {
>>> This check looks suspiscious to me. In our case the len is not
>>> modified by the previous translation and it fails, I don't see why. It
>>> should be valid to be able to notify 5 granules.
>>
>> So after discussion with Alex, looks the way we notify the host currently is
>> wrong. we set the addr_mask to the mapping/unmapping size
>> -1 whereas this should be a page mask instead (granule size or block size?).
>> So if the guest maps 5 x 4kB pages we should send 5 notifications for each
>> page and not a single one. It is unclear to me if we can notify with
>> hugepage/block page size mask. Peter may confirm/infirm this. in vsmmuv3
>> code I notify by granule or block size.
>>
>> Bharat, please can you add this to your TODO list?
>>
>> Linu, thanks a lot for the time you spent debugging this issue.
>> Curiously on my side, it is really seldom hit but it is ...
> 
> Thanks Linu and Eric, I added this to my todo list.
> While I am still not able to reproduce the issue.  I tried with e1000 and now try with ixgbe device. May I know which device can be used to reproduce this issue?

On my side I used an i350T2 device (igb) to reproduce the issue.

Thanks

Eric
> 
> Thanks
> -Bharat
> 
>>
>> Thanks!
>>
>> Eric
>>>
>>> Thanks
>>>
>>> Eric
>>>>>>         error_report("iommu has granularity incompatible with target AS");
>>>>>>         return false;
>>>>>>     }
>>>>>>
>>>>>> Just trying to understand how this is not hitting in your case.
>>>>>>
>>>>>>
>>>>>
>>>>
>>>
>