Re: [PATCH v4 00/41] vfio: Adopt iommufd

[Matthew Rosato]

On 11/7/23 1:28 PM, Cédric Le Goater wrote:
> On 11/2/23 08:12, Zhenzhong Duan wrote:
>> Hi,
>>
>> Thanks all for giving guides and comments on previous series, here is
>> the v4 of pure iommufd support part.
>>
>> Based on Cédric's suggestion, this series includes an effort to remove
>> spapr code from container.c, now all spapr functions are moved to spapr.c
>> or spapr_pci_vfio.c, but there are still a few trival check on
>> VFIO_SPAPR_TCE_*_IOMMU which I am not sure if deserved to introduce many
>> callbacks and duplicate code just to remove them. Some functions are moved
>> to spapr.c instead of spapr_pci_vfio.c to avoid compile issue because
>> spapr_pci_vfio.c is arch specific, or else we need to introduce stub
>> functions to those spapr functions moved.
>>
>>
>> PATCH 1-5: Move spapr functions to spapr*.c
>> PATCH 6-20: Abstract out base container
>> PATCH 21-24: Introduce sparpr container and its specific interface
> 
> PATCH 6-24 applied to vfio-next :
> 
>   https://github.com/legoater/qemu/commits/vfio-next
> 
> (with a global s/fucntional/functional/)
> 
> 
> I also pushed the remaining patches on :
> 
>   https://github.com/legoater/qemu/commits/vfio-8.2
> 
> with a slight rework of the IOMMUFD configuration, now done per platform.
> The VFIO frontend and the 'iommufd' object are only available on x86_64,
> arm, s390x.

FYI, I first tried this vfio-8.2 branch on s390x but wasn't actually able to 
use the iommufd backend (was getting errors like Property 'vfio-pci.iommufd' 
not found) so I think something isn't actually enabling IOMMUFD as expected 
with your change...

Instead I tested on s390x using vfio-next + patches 25-41 of this series on 
top.  

Legacy backend regression testing worked fine for vfio-pci, vfio-ap and 
vfio-ccw.

Using iommufd backend for vfio-pci on s390 exposes an s390-only issue related 
to accounting of vfio DMA limit (code in hw/s390x/s390-pci-vfio.c assumes 
VFIODevice.group is never null, but that's no longer true when we use the 
iommufd backend with cdev).  We don't even need to track this when using the 
iommufd backend -- With that issue bypassed, vfio-pci testing on s390x looks 
good so far.  I'll send a separate fix for that.

Using the iommufd backend for vfio-ccw and vfio-ap did not work, see response 
to patch 28.

Thanks,
Matt