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Date:   Thu, 20 Oct 2022 08:05:20 -0300
From:   Jason Gunthorpe <jgg@nvidia.com>
To:     Niklas Schnelle <schnelle@linux.ibm.com>
Cc:     Matthew Rosato <mjrosato@linux.ibm.com>, iommu@lists.linux.dev,
        Joerg Roedel <joro@8bytes.org>, Will Deacon <will@kernel.org>,
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Subject: Re: [PATCH 3/5] iommu/s390: Use RCU to allow concurrent domain_list
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On Thu, Oct 20, 2022 at 10:51:10AM +0200, Niklas Schnelle wrote:

> Ok that makes sense thanks for the explanation. So yes my assessment is
> still that in this situation the IOTLB flush is architected to return
> an error that we can ignore. Not the most elegant I admit but at least
> it's simple. Alternatively I guess we could use call_rcu() to do the
> zpci_unregister_ioat() but I'm not sure how to then make sure that a
> subsequent zpci_register_ioat() only happens after that without adding
> too much more logic.

This won't work either as the domain could have been freed before the
call_rcu() happens, the domain needs to be detached synchronously

Jason