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Message-ID: <Y1ErcEe82yjJI+ET@nvidia.com>
Date: Thu, 20 Oct 2022 08:05:20 -0300
From: Jason Gunthorpe <jgg@...dia.com>
To: Niklas Schnelle <schnelle@...ux.ibm.com>
Cc: Matthew Rosato <mjrosato@...ux.ibm.com>, iommu@...ts.linux.dev,
Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
Robin Murphy <robin.murphy@....com>,
Gerd Bayer <gbayer@...ux.ibm.com>,
Pierre Morel <pmorel@...ux.ibm.com>,
linux-s390@...r.kernel.org, borntraeger@...ux.ibm.com,
hca@...ux.ibm.com, gor@...ux.ibm.com,
gerald.schaefer@...ux.ibm.com, agordeev@...ux.ibm.com,
svens@...ux.ibm.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/5] iommu/s390: Use RCU to allow concurrent domain_list
iteration
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
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