Re: [PATCH v4 1/5] iommu/s390: Fix duplicate domain attachments

[Jason Gunthorpe <jgg@nvidia.com>]

On Tue, Oct 04, 2022 at 02:07:02PM +0200, Niklas Schnelle wrote:
> Since commit fa7e9ecc5e1c ("iommu/s390: Tolerate repeat attach_dev
> calls") we can end up with duplicates in the list of devices attached to
> a domain. This is inefficient and confusing since only one domain can
> actually be in control of the IOMMU translations for a device. Fix this
> by detaching the device from the previous domain, if any, on attach.
> Add a WARN_ON() in case we still have attached devices on freeing the
> domain. While here remove the re-attach on failure dance as it was
> determined to be unlikely to help and may confuse debug and recovery.
> 
> Fixes: fa7e9ecc5e1c ("iommu/s390: Tolerate repeat attach_dev calls")
> Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com>
> ---
> v3 -> v4:
> - Drop s390_domain from __s390_iommu_detach_device() (Jason)
> - WARN_ON() mismatched domain in s390_iommu_detach_device() (Jason)
> - Use __s390_iommu_detach_device() in s390_iommu_release_device() (Jason)

Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>

Jason