Re: [PATCH 0/4] Fix splats releated to using the iommu_group after destroying devices

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

On 9/8/22 2:44 PM, Jason Gunthorpe wrote:
> The basic issue is that the iommu_group is being used by VFIO after all
> the device drivers have been removed.
> 
> In part this is caused by bad logic inside the iommu core that doesn't
> sequence removing the device from the group properly, and in another part
> this is bad logic in VFIO continuing to use device->iommu_group after all
> VFIO device drivers have been removed.
> 
> Fix both situations. Either fix alone should fix the bug reported, but
> both together bring a nice robust design to this area.
> 
> This is a followup from this thread:
> 
> https://lore.kernel.org/kvm/20220831201236.77595-1-mjrosato@linux.ibm.com/
> 
> Matthew confirmed an earlier version of the series solved the issue, it
> would be best if he would test this as well to confirm the various changes
> are still OK.

FYI I've been running this series (+ the incremental to patch 4 you mentioned) against my original repro scenario in a loop overnight, looks good.

> 
> The iommu patch is independent of the other patches, it can go through the
> iommu rc tree.
> 
> Jason Gunthorpe (4):
>   vfio: Simplify vfio_create_group()
>   vfio: Move the sanity check of the group to vfio_create_group()
>   vfio: Follow a strict lifetime for struct iommu_group *
>   iommu: Fix ordering of iommu_release_device()
> 
>  drivers/iommu/iommu.c    |  36 ++++++--
>  drivers/vfio/vfio_main.c | 172 +++++++++++++++++++++------------------
>  2 files changed, 120 insertions(+), 88 deletions(-)
> 
> 
> base-commit: 245898eb9275ce31942cff95d0bdc7412ad3d589