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Re: [PATCH v3 2/6] xen: pci: introduce reference counting for pdev
- To: Roger Pau Monné <roger.pau@xxxxxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Mon, 17 Apr 2023 12:34:31 +0200
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- Cc: "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, George Dunlap <george.dunlap@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Paul Durrant <paul@xxxxxxx>, Kevin Tian <kevin.tian@xxxxxxxxx>
- Delivery-date: Mon, 17 Apr 2023 10:34:51 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 17.04.2023 12:17, Roger Pau Monné wrote:
> On Fri, Apr 14, 2023 at 01:30:39AM +0000, Volodymyr Babchuk wrote:
>> Above I have proposed another view on this. I hope, it will work for
>> you. Just to reiterate, idea is to allow "harmless" refcounts to be left
>> after returning from pci_remove_device(). By "harmless" I mean that
>> owners of those refcounts will not try to access the physical PCI
>> device if pci_remove_device() is already finished.
>
> I'm not strictly a maintainer of this piece code, albeit I have an
> opinion. I will like to also hear Jans opinion, since he is the
> maintainer.
I'm afraid I can't really appreciate the term "harmless refcounts". Whoever
holds a ref is entitled to access the device. As stated before, I see only
two ways of getting things consistent: Either pci_remove_device() is
invoked upon dropping of the last ref, or it checks that it is dropping the
last one. The former looks architecturally cleaner to me, but I can accept
that moving there might be more of a change, so wouldn't object to going
the latter route.
Jan
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