Re: [PATCH v7 1/6] iommu/s390: Fix duplicate domain attachments

[Jason Gunthorpe <jgg@nvidia.com>]

On Mon, Oct 17, 2022 at 02:45:53PM +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>
> Reviewed-by: Matthew Rosato <mjrosato@linux.ibm.com>
> ---
> v6->v7:
> - Added Matt's R-b
> v5->v6:
> - Only set zdev->dma_table once zpci_register_ioat() succeeded (Matt)
> v4->v5:
> - Unregister IOAT and set zdev->dma_table on error (Matt)

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

Jason