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SubjectRe: [PATCH v10 13/26] s390: vfio-ap: zeroize the AP queues
On Wed, 12 Sep 2018 15:43:03 -0400
Tony Krowiak <akrowiak@linux.vnet.ibm.com> wrote:

> From: Tony Krowiak <akrowiak@linux.ibm.com>
>
> Let's call PAPQ(ZAPQ) to zeroize a queue for each queue configured
> for a mediated matrix device when it is released.
>
> Zeroizing a queue resets the queue, clears all pending
> messages for the queue entries and disables adapter interruptions
> associated with the queue.
>
> Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com>
> Reviewed-by: Halil Pasic <pasic@linux.ibm.com>
> Tested-by: Michael Mueller <mimu@linux.ibm.com>
> Tested-by: Farhan Ali <alifm@linux.ibm.com>
> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
> ---
> drivers/s390/crypto/vfio_ap_ops.c | 44 +++++++++++++++++++++++++++++++++++++
> 1 files changed, 44 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
> index f8b276a..48b1b78 100644
> --- a/drivers/s390/crypto/vfio_ap_ops.c
> +++ b/drivers/s390/crypto/vfio_ap_ops.c
> @@ -829,6 +829,49 @@ static int vfio_ap_mdev_group_notifier(struct notifier_block *nb,
> return NOTIFY_OK;
> }
>
> +static int vfio_ap_mdev_reset_queue(unsigned int apid, unsigned int apqi,
> + unsigned int retry)
> +{
> + struct ap_queue_status status;
> +
> + do {
> + status = ap_zapq(AP_MKQID(apid, apqi));
> + switch (status.response_code) {
> + case AP_RESPONSE_NORMAL:
> + return 0;
> + case AP_RESPONSE_RESET_IN_PROGRESS:
> + case AP_RESPONSE_BUSY:
> + msleep(20);
> + break;
> + default:
> + /* things are really broken, give up */
> + return -EIO;
> + }
> + } while (retry--);
> +
> + return -EBUSY;

So, this function may either return 0, -EIO (things are really broken),
or -EBUSY (still busy after multiple tries)...

> +}
> +
> +static int vfio_ap_mdev_reset_queues(struct mdev_device *mdev)
> +{
> + int ret;
> + int rc = 0;
> + unsigned long apid, apqi;
> + struct ap_matrix_mdev *matrix_mdev = mdev_get_drvdata(mdev);
> +
> + for_each_set_bit_inv(apid, matrix_mdev->matrix.apm,
> + matrix_mdev->matrix.apm_max + 1) {
> + for_each_set_bit_inv(apqi, matrix_mdev->matrix.aqm,
> + matrix_mdev->matrix.aqm_max + 1) {
> + ret = vfio_ap_mdev_reset_queue(apid, apqi, 1);
> + if (ret)
> + rc = ret;

...and here, we return the last error of any of the resets. Two
questions:

- Does it make sense to continue if we get -EIO? IOW, does "really
broken" only refer to a certain tuple and other tuples still can/need
to be reset?
- Is the return code useful in any way, as we don't know which tuple it
refers to?

> + }
> + }
> +
> + return rc;
> +}
> +
> static int vfio_ap_mdev_open(struct mdev_device *mdev)
> {
> struct ap_matrix_mdev *matrix_mdev = mdev_get_drvdata(mdev);
> @@ -859,6 +902,7 @@ static void vfio_ap_mdev_release(struct mdev_device *mdev)
> if (matrix_mdev->kvm)
> kvm_arch_crypto_clear_masks(matrix_mdev->kvm);
>
> + vfio_ap_mdev_reset_queues(mdev);
> vfio_unregister_notifier(mdev_dev(mdev), VFIO_GROUP_NOTIFY,
> &matrix_mdev->group_notifier);
> matrix_mdev->kvm = NULL;

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