Re: S390 testing for IOMMUFD

[Matthew Rosato <mjrosato@linux.ibm.com>]

On 11/7/22 8:09 PM, Jason Gunthorpe wrote:
> On Mon, Nov 07, 2022 at 08:48:53PM -0400, Jason Gunthorpe wrote:
>> [
>> This has been in linux-next for a little while now, and we've completed
>> the syzkaller run. 1300 hours of CPU time have been invested since the
>> last report with no improvement in coverage or new detections. syzkaller
>> coverage reached 69%(75%), and review of the misses show substantial
>> amounts are WARN_ON's and other debugging which are not expected to be
>> covered.
>> ]
>>
>> iommufd is the user API to control the IOMMU subsystem as it relates to
>> managing IO page tables that point at user space memory.
> 
> [chop cc list]
> 
> s390 mdev maintainers,
> 
> Can I ask your help to test this with the two S390 mdev drivers? Now
> that gvt is passing and we've covered alot of the QA ground it is a
> good time to run it.
> 
> Take the branch from here:
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/jgg/iommufd.git/log/?h=for-next
> 
> And build the kernel with 
> 
> CONFIG_VFIO_CONTAINER=n
> CONFIG_IOMMUFD=y
> CONFIG_IOMMUFD_VFIO_CONTAINER=y
> 
> And your existing stuff should work with iommufd providing the iommu
> support to vfio. There will be a dmesg confirming this.
> 
> Let me know if there are any problems!

FWIW, vfio-pci via s390 is working fine so far, though I'll put it through more paces over the next few weeks and report if I find anything.

As far as mdev drivers...  

-ccw: Sounds like Eric is already aware there is an issue and is investigating (I see errors as well).

-ap: I see the exact same issue that Christian mentioned...  I'll talk to Tony & Jason about it.

> 
> If I recall there was some desire from the S390 platform team to start
> building on iommufd to create some vIOMMU acceleration for S390
> guests, this is a necessary first step.

There's probably something here for -ccw in the future, but you might be thinking of s390 vfio-pci e.g. to implement the in-kernel handling of nested mappings on s390 -- yep, work in in progress here, not ready for sharing yet but I have been most recently basing my work on top of the nesting series https://github.com/yiliu1765/iommufd/tree/iommufd-v6.0-rc3-nesting

Matt