Re: [PATCH v7 17/22] vfio-pci/zdev: add open/close device hooks

[Matthew Rosato]

On 5/16/22 2:35 PM, Jason Gunthorpe wrote:
> On Mon, May 16, 2022 at 02:30:46PM -0400, Matthew Rosato wrote:
>
> > Conceptually I think this would work for QEMU anyway (it always sets the kvm
> > before we open the device).  I tried to test the idea quickly but couldn't
> > get the following to apply on vfio-next or your vfio_group_locking -- but I
> > understand what you're trying to do so I'll re-work and try it out.
>
> I created it on 8c9350e9bf43de1ebab3cc8a80703671e6495ab4 which is the
> vfio_group_locking.. I can send you a github if it helps
> https://github.com/jgunthorpe/linux/commits/vfio_group_lockin
Thanks -- I was able to successfully test your proposed idea (+ some 
changes to make it compile :)) on top of vfio_group_locking along with a 
modified version of my zdev series.  I also tried it out with vfio-ap 
successfully, but have nothing to test GVT with.

That said, this has caused me to realize that 'iommu: 
iommu_group_claim_dma_owner() must always assign a domain' breaks s390x 
vfio-pci :( I wonder if it is due to the way s390x PCI currently 
switches between dma ops and iommu ops.  It looks like it breaks vfio-ap 
mdevs too, but I know less about that --  I will have to investigate 
both more tomorrow.