From: Halil Pasic <pasic@linux.ibm.com>
To: "Jason J. Herne" <jjherne@linux.ibm.com>
Cc: Tony Krowiak <akrowiak@linux.ibm.com>,
linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org,
kvm@vger.kernel.org, freude@linux.ibm.com,
borntraeger@de.ibm.com, cohuck@redhat.com,
mjrosato@linux.ibm.com, alex.williamson@redhat.com,
kwankhede@nvidia.com, fiuczy@linux.ibm.com,
Halil Pasic <pasic@linux.ibm.com>
Subject: Re: [PATCH v18 08/18] s390/vfio-ap: allow assignment of unavailable AP queues to mdev device
Date: Wed, 9 Mar 2022 01:56:22 +0100 [thread overview]
Message-ID: <20220309015623.41543d75.pasic@linux.ibm.com> (raw)
In-Reply-To: <439f929f-9d15-c33c-b40d-88dd06cebd85@linux.ibm.com>
On Tue, 8 Mar 2022 10:39:09 -0500
"Jason J. Herne" <jjherne@linux.ibm.com> wrote:
> On 3/7/22 07:31, Tony Krowiak wrote:
> >>> + * If the input apm and aqm belong to the matrix_mdev's matrix,
> >>> + * then move on to the next.
> >>> + */
> >>> + if (mdev_apm == matrix_mdev->matrix.apm &&
> >>> + mdev_aqm == matrix_mdev->matrix.aqm)
> >>> continue;
> >>
> >> We may have a problem here. This check seems like it exists to stop you from
> >> comparing an mdev's apm/aqm with itself. Obviously comparing an mdev's newly
> >> updated apm/aqm with itself would cause a false positive sharing check, right?
> >> If this is the case, I think the comment should be changed to reflect that.
> >
> > You are correct, this check is performed to prevent comparing an mdev to
> > itself, I'll improve the comment.
> >
> >>
> >> Aside from the comment, what stops this particular series of if statements from
> >> allowing us to configure a second mdev with the exact same apm/aqm values as an
> >> existing mdev? If we do, then this check's continue will short circuit the rest
> >> of the function thereby allowing that 2nd mdev even though it should be a
> >> sharing violation.
> >
> > I don't see how this is possible.
>
> You are correct. I missed the fact that you are comparing pointers here, and not
> values. Apologies. Now that I understand the code, I agree that this is fine as is.
>
I believe clarifying the 'belongs to' vs 'is a part of' stuff is still
worthwhile, because 'belongs to' does beg the question you asked. Thus
IMHO it is good that you raised the question.
Regards,
Halil
next prev parent reply other threads:[~2022-03-09 1:13 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-15 0:50 [PATCH v18 00/17] s390/vfio-ap: dynamic configuration support Tony Krowiak
2022-02-15 0:50 ` [PATCH v18 01/18] s390/ap: driver callback to indicate resource in use Tony Krowiak
2022-02-15 0:50 ` [PATCH v18 02/18] s390/ap: notify drivers on config changed and scan complete callbacks Tony Krowiak
2022-02-15 0:50 ` [PATCH v18 03/18] s390/vfio-ap: use new AP bus interface to search for queue devices Tony Krowiak
2022-02-15 0:50 ` [PATCH v18 04/18] s390/vfio-ap: move probe and remove callbacks to vfio_ap_ops.c Tony Krowiak
2022-02-15 0:50 ` [PATCH v18 05/18] s390/vfio-ap: manage link between queue struct and matrix mdev Tony Krowiak
2022-02-15 0:50 ` [PATCH v18 06/18] s390/vfio-ap: introduce shadow APCB Tony Krowiak
2022-02-15 0:50 ` [PATCH v18 07/18] s390/vfio-ap: refresh guest's APCB by filtering APQNs assigned to mdev Tony Krowiak
2022-03-02 19:35 ` Jason J. Herne
2022-03-02 23:43 ` Tony Krowiak
2022-02-15 0:50 ` [PATCH v18 08/18] s390/vfio-ap: allow assignment of unavailable AP queues to mdev device Tony Krowiak
2022-03-03 15:39 ` Jason J. Herne
2022-03-07 12:31 ` Tony Krowiak
2022-03-07 13:27 ` Halil Pasic
2022-03-07 14:10 ` Tony Krowiak
2022-03-07 17:10 ` Halil Pasic
2022-03-07 23:45 ` Tony Krowiak
2022-03-08 10:06 ` Halil Pasic
2022-03-08 15:36 ` Tony Krowiak
2022-03-08 15:39 ` Jason J. Herne
2022-03-09 0:56 ` Halil Pasic [this message]
2022-02-15 0:50 ` [PATCH v18 09/18] s390/vfio-ap: introduce new mutex to control access to the KVM pointer Tony Krowiak
2022-02-15 0:50 ` [PATCH v18 10/18] s390/vfio-ap: allow hot plug/unplug of AP devices when assigned/unassigned Tony Krowiak
2022-03-11 14:26 ` Jason J. Herne
2022-03-11 16:07 ` Tony Krowiak
2022-03-14 13:17 ` Jason J. Herne
2022-03-18 17:30 ` Tony Krowiak
2022-02-15 0:50 ` [PATCH v18 11/18] s390/vfio-ap: hot plug/unplug of AP devices when probed/removed Tony Krowiak
2022-02-15 0:50 ` [PATCH v18 12/18] s390/vfio-ap: reset queues after adapter/domain unassignment Tony Krowiak
2022-03-15 14:13 ` Jason J. Herne
2022-03-18 17:54 ` Tony Krowiak
2022-03-18 22:13 ` Tony Krowiak
2022-02-15 0:50 ` [PATCH v18 13/18] s390/vfio-ap: implement in-use callback for vfio_ap driver Tony Krowiak
2022-03-22 13:13 ` Jason J. Herne
2022-03-22 13:30 ` Tony Krowiak
2022-02-15 0:50 ` [PATCH v18 14/18] s390/vfio-ap: sysfs attribute to display the guest's matrix Tony Krowiak
2022-03-22 13:22 ` Jason J. Herne
2022-03-22 13:41 ` Tony Krowiak
2022-02-15 0:50 ` [PATCH v18 15/18] s390/vfio-ap: handle config changed and scan complete notification Tony Krowiak
2022-03-24 14:09 ` Jason J. Herne
2022-03-30 19:26 ` Tony Krowiak
2022-02-15 0:50 ` [PATCH v18 16/18] s390/vfio-ap: update docs to include dynamic config support Tony Krowiak
2022-02-15 0:50 ` [PATCH v18 17/18] s390/Docs: new doc describing lock usage by the vfio_ap device driver Tony Krowiak
2022-03-31 0:28 ` Halil Pasic
2022-04-04 21:34 ` Tony Krowiak
2022-04-06 8:23 ` Halil Pasic
2022-02-15 0:50 ` [PATCH v18 18/18] MAINTAINERS: pick up all vfio_ap docs for VFIO AP maintainers Tony Krowiak
2022-02-22 19:09 ` [PATCH v18 00/17] s390/vfio-ap: dynamic configuration support Tony Krowiak
2022-02-28 15:53 ` Tony Krowiak
2022-03-02 14:10 ` Jason J. Herne
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