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SubjectRe: [PATCH v2 1/7] s390: vfio-ap: wait for queue empty on queue reset
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On 03/05/2019 23:14, Tony Krowiak wrote:
> Refactors the AP queue reset function to wait until the queue is empty
> after the PQAP(ZAPQ) instruction is executed to zero out the queue as
> required by the AP architecture.
>
> Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com>
> ---
> drivers/s390/crypto/vfio_ap_ops.c | 35 ++++++++++++++++++++++++++++++++---
> 1 file changed, 32 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
> index 900b9cf20ca5..b88a2a2ba075 100644
> --- a/drivers/s390/crypto/vfio_ap_ops.c
> +++ b/drivers/s390/crypto/vfio_ap_ops.c
> @@ -271,6 +271,32 @@ static int vfio_ap_mdev_verify_no_sharing(struct ap_matrix_mdev *matrix_mdev)
> return 0;
> }
>
> +static void vfio_ap_mdev_wait_for_qempty(unsigned long apid, unsigned long apqi)
> +{
> + struct ap_queue_status status;
> + ap_qid_t qid = AP_MKQID(apid, apqi);
> + int retry = 5;
> +
> + do {
> + status = ap_tapq(qid, NULL);
> + switch (status.response_code) {
> + case AP_RESPONSE_NORMAL:
> + if (status.queue_empty)
> + return;
> + msleep(20);

NIT: Fall through ?

> + break;
> + case AP_RESPONSE_RESET_IN_PROGRESS:
> + case AP_RESPONSE_BUSY:
> + msleep(20);
> + break;
> + default:
> + pr_warn("%s: tapq err %02x: %04lx.%02lx may not be empty\n",
> + __func__, status.response_code, apid, apqi);

I do not thing the warning sentence is appropriate:
The only possible errors here are if the AP is not available due to AP
checkstop, deconfigured AP or invalid APQN.


> + return;
> + }
> + } while (--retry);
> +}
> +
> /**
> * assign_adapter_store
> *
> @@ -790,15 +816,18 @@ 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)
> +int vfio_ap_mdev_reset_queue(unsigned int apid, unsigned int apqi)
> {
> struct ap_queue_status status;
> + int retry = 5;
>
> do {
> status = ap_zapq(AP_MKQID(apid, apqi));
> switch (status.response_code) {
> case AP_RESPONSE_NORMAL:
> + vfio_ap_mdev_wait_for_qempty(apid, apqi);
> + return 0;
> + case AP_RESPONSE_DECONFIGURED:

Since you modify the switch, you can return for all the following cases:
AP_RESPONSE_DECONFIGURE
..._CHECKSTOP
..._INVALID_APQN


And you should wait for qempty on AP_RESET_IN_PROGRESS along with
AP_RESPONSE_NORMAL

> return 0;
> case AP_RESPONSE_RESET_IN_PROGRESS:
> case AP_RESPONSE_BUSY:

While at modifying this function, the AP_RESPONSE_BUSY is not a valid
code for ZAPQ, you can remove this.

> @@ -824,7 +853,7 @@ static int vfio_ap_mdev_reset_queues(struct mdev_device *mdev)
> 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);
> + ret = vfio_ap_mdev_reset_queue(apid, apqi);

IMHO, since you are at changing this call, passing the apqn as parameter
would be a good simplification.



> /*
> * Regardless whether a queue turns out to be busy, or
> * is not operational, we need to continue resetting

Depends on why the reset failed, but this is out of scope.

>


--
Pierre Morel
Linux/KVM/QEMU in Böblingen - Germany

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