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Date:   Thu, 5 Jan 2023 20:32:38 -0400
From:   Jason Gunthorpe <jgg@nvidia.com>
To:     Matthew Rosato <mjrosato@linux.ibm.com>
Cc:     Alex Williamson <alex.williamson@redhat.com>, cohuck@redhat.com,
        borntraeger@linux.ibm.com, jjherne@linux.ibm.com,
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        Kevin Tian <kevin.tian@intel.com>,
        Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH v3 1/1] vfio: remove VFIO_GROUP_NOTIFY_SET_KVM
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On Thu, Jan 05, 2023 at 07:16:37PM -0500, Matthew Rosato wrote:

> Yeah, this is also what I was thinking, replace the direct
> kvm_put_kvm calls with, say, schedule_delayed_work in each driver,
> where the delayed task just does the kvm_put_kvm (along with a brief
> comment explaining why we handle the put asynchronously).

Don't put that in every driver, do something like mmput_async() where
the core code has all of this.

> Other than that..  The goal of this patch originally was to get the
> kvm reference at first open_device and release it with the very last
> close_device, so the only other option I could think of would be to
> take the responsibility back from the vfio drivers and do the
> kvm_get_kvm and kvm_put_kvm directly in vfio_main after dropping the
> (but that would result in some ugly symbol linkage and would acquire
> kvm references that a driver maybe does not care about so I don't
> really like that idea)

And we still have the deadlock problem anyhow..

Jason