Messages in this thread | | | Date | Mon, 7 Mar 2022 09:10:29 -0500 | Subject | Re: [PATCH v18 08/18] s390/vfio-ap: allow assignment of unavailable AP queues to mdev device | From | Tony Krowiak <> |
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On 3/7/22 08:27, Halil Pasic wrote: > On Mon, 7 Mar 2022 07:31:21 -0500 > Tony Krowiak <akrowiak@linux.ibm.com> wrote: > >> On 3/3/22 10:39, Jason J. Herne wrote: >>> On 2/14/22 19:50, Tony Krowiak wrote: >>>> /** >>>> - * vfio_ap_mdev_verify_no_sharing - verifies that the AP matrix is >>>> not configured >>>> + * vfio_ap_mdev_verify_no_sharing - verify APQNs are not shared by >>>> matrix mdevs >>>> * >>>> - * @matrix_mdev: the mediated matrix device >>>> + * @mdev_apm: mask indicating the APIDs of the APQNs to be verified >>>> + * @mdev_aqm: mask indicating the APQIs of the APQNs to be verified >>>> * >>>> - * Verifies that the APQNs derived from the cross product of the AP >>>> adapter IDs >>>> - * and AP queue indexes comprising the AP matrix are not configured >>>> for another >>>> + * Verifies that each APQN derived from the Cartesian product of a >>>> bitmap of >>>> + * AP adapter IDs and AP queue indexes is not configured for any matrix >>>> * mediated device. AP queue sharing is not allowed. >>>> * >>>> - * Return: 0 if the APQNs are not shared; otherwise returns >>>> -EADDRINUSE. >>>> + * Return: 0 if the APQNs are not shared; otherwise return -EADDRINUSE. >>>> */ >>>> -static int vfio_ap_mdev_verify_no_sharing(struct ap_matrix_mdev >>>> *matrix_mdev) >>>> +static int vfio_ap_mdev_verify_no_sharing(unsigned long *mdev_apm, >>>> + unsigned long *mdev_aqm) >>>> { >>>> - struct ap_matrix_mdev *lstdev; >>>> + struct ap_matrix_mdev *matrix_mdev; >>>> DECLARE_BITMAP(apm, AP_DEVICES); >>>> DECLARE_BITMAP(aqm, AP_DOMAINS); >>>> - list_for_each_entry(lstdev, &matrix_dev->mdev_list, node) { >>>> - if (matrix_mdev == lstdev) >>>> + list_for_each_entry(matrix_mdev, &matrix_dev->mdev_list, node) { >>>> + /* >>>> + * If the input apm and aqm belong to the matrix_mdev's matrix, > How about: > > s/belong to the matrix_mdev's matrix/are fields of the matrix_mdev > object/
This is the comment I wrote:
/* * Comparing an mdev's newly updated apm/aqm with itself would * result in a false positive when verifying whether any APQNs * are shared; so, if the input apm and aqm belong to the * matrix_mdev's matrix, then move on to the next one. */
However, I'd be happy to change it to whatever either of you want.
> > >>>> + * 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. > I agree with Tony and his explanation. > > Furthermore IMHO is relates to the class identity vs equality problem, in > a sense that identity always implies equality. > > Regards, > Halil
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