From: Halil Pasic <pasic@linux.ibm.com>
To: Tony Krowiak <akrowiak@linux.ibm.com>
Cc: linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org,
kvm@vger.kernel.org, borntraeger@de.ibm.com, cohuck@redhat.com,
alex.williamson@redhat.com, kwankhede@nvidia.com,
david@redhat.com
Subject: Re: [PATCH] s390/vfio-ap: Clean up vfio_ap resources when KVM pointer invalidated
Date: Mon, 7 Dec 2020 16:24:11 +0100 [thread overview]
Message-ID: <20201207162411.050c6cea.pasic@linux.ibm.com> (raw)
In-Reply-To: <a5a613ef-4c74-ad68-46bd-7159fbafef47@linux.ibm.com>
On Fri, 4 Dec 2020 11:48:24 -0500
Tony Krowiak <akrowiak@linux.ibm.com> wrote:
> On 12/3/20 12:55 PM, Halil Pasic wrote:
> > On Wed, 2 Dec 2020 18:41:01 -0500
> > Tony Krowiak <akrowiak@linux.ibm.com> wrote:
> >
> >> The vfio_ap device driver registers a group notifier with VFIO when the
> >> file descriptor for a VFIO mediated device for a KVM guest is opened to
> >> receive notification that the KVM pointer is set (VFIO_GROUP_NOTIFY_SET_KVM
> >> event). When the KVM pointer is set, the vfio_ap driver stashes the pointer
> >> and calls the kvm_get_kvm() function to increment its reference counter.
> >> When the notifier is called to make notification that the KVM pointer has
> >> been set to NULL, the driver should clean up any resources associated with
> >> the KVM pointer and decrement its reference counter. The current
> >> implementation does not take care of this clean up.
> >>
> >> Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com>
> > Do we need a Fixes tag? Do we need this backported? In my opinion
> > this is necessary since the interrupt patches.
>
> I'll put in a fixes tag:
> Fixes: 258287c994de (s390: vfio-ap: implement mediated device open callback)
>
> Yes, this should probably be backported.
I changed my mind regarding the severity of this issue. I was paranoid
about post-mortem interrupts, and resulting notifier byte updates by the
machine. What I overlooked is that the pin is going to prevent the memory
form getting repurposed. I.e. if we have something like vmalloc(),
vfio_pin(notifier_page), vfree(), I believe the notifier_page is not free
(available for allocation). So the worst case scenario is IMHO a resource
leak and not corruption. So I'm not sure this must be backported.
Opinions?
Regards,
Halil
next prev parent reply other threads:[~2020-12-07 15:25 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-02 23:41 [PATCH] s390/vfio-ap: Clean up vfio_ap resources when KVM pointer invalidated Tony Krowiak
2020-12-03 10:19 ` Cornelia Huck
2020-12-03 17:01 ` Halil Pasic
2020-12-03 19:14 ` Tony Krowiak
2020-12-03 17:55 ` Halil Pasic
2020-12-04 14:43 ` Tony Krowiak
2020-12-04 19:05 ` Halil Pasic
2020-12-04 19:46 ` Tony Krowiak
2020-12-04 21:54 ` Halil Pasic
2020-12-07 18:50 ` Tony Krowiak
2020-12-08 0:01 ` Halil Pasic
[not found] ` <e196b743-74d8-398b-4b3e-4a64002d9bfc@linux.ibm.com>
2020-12-13 22:57 ` Halil Pasic
2020-12-04 16:48 ` Tony Krowiak
2020-12-04 16:57 ` Cornelia Huck
2020-12-04 19:47 ` Tony Krowiak
2020-12-07 15:24 ` Halil Pasic [this message]
2020-12-07 15:42 ` Christian Borntraeger
2020-12-07 19:05 ` Tony Krowiak
2020-12-08 0:40 ` Halil Pasic
2020-12-11 21:08 ` Tony Krowiak
2020-12-13 23:13 ` Halil Pasic
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