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Date:   Mon, 5 Sep 2022 06:32:15 -0500
From:   Bjorn Helgaas <helgaas@kernel.org>
To:     Alex Williamson <alex.williamson@redhat.com>
Cc:     a.dibacco.ks@gmail.com, Cornelia Huck <cohuck@redhat.com>,
        kvm@vger.kernel.org, linux-pci@vger.kernel.org
Subject: [bugzilla-daemon@kernel.org: [Bug 216449] New: vfio-pci calls
 pci_bus_reset whenever a pci_release is triggered and refcnt is zero]
Message-ID: <20220905113215.GA584198@bhelgaas>
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----- Forwarded message from bugzilla-daemon@kernel.org -----

https://bugzilla.kernel.org/show_bug.cgi?id=216449

I'm using vfio-pci to map an FPGA. I have an utility program that gets a file
descriptor for the device and does an mmap to read and write registers.

When I close the utility the FPGA is reset and all registers are gone. 
I wonder if this is the correct behaviour, I understand that the
vfio_pci_try_bus_reset is performed only when refcnt reaches zero but, in case
of other drivers, like UIO the behaviour is different. 

I expected to be able to close my utility and restart it and find the FPGA
registers at the last configured value.

The vfio_pci_try_bus_reset is in vfio_pci_disable that is called by
pci_release.

Probably even a module parameter to prevent calling vfio_pci_try_bus_reset
could be useful.