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Date:   Tue, 3 Apr 2018 13:17:59 +0200
From:   Cornelia Huck <cohuck@redhat.com>
To:     Tony Krowiak <akrowiak@linux.vnet.ibm.com>
Cc:     linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org,
        kvm@vger.kernel.org, freude@de.ibm.com, schwidefsky@de.ibm.com,
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Subject: Re: [PATCH v3 09/14] s390: vfio-ap: sysfs interfaces to configure
 domains
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On Wed, 14 Mar 2018 14:25:49 -0400
Tony Krowiak <akrowiak@linux.vnet.ibm.com> wrote:

> Provides the sysfs interfaces for assigning AP domains to
> and unassigning AP domains from a mediated matrix device.
> 
> An AP domain ID corresponds to an AP queue index (APQI). For
> each domain assigned to the mediated matrix device, its
> corresponging APQI is stored in an AP queue mask (AQM).
> The bits in the AQM, from most significant to least
> significant bit, correspond to AP domain numbers 0 to 255.
> When a domain is assigned, the bit corresponding to its
> APQI will be set in the AQM. Likewise, when a domain is
> unassigned, the bit corresponding to its APQI will be
> cleared from the AQM.
> 
> The relevant sysfs structures are:
> 
> /sys/devices/vfio_ap
> ... [matrix]
> ...... [mdev_supported_types]
> ......... [vfio_ap-passthrough]
> ............ [devices]
> ...............[$uuid]
> .................. assign_domain
> .................. unassign_domain
> 
> To assign a domain to the $uuid mediated matrix device,
> write the domain's ID to the assign_domain file. To
> unassign a domain, write the domain's ID to the
> unassign_domain file. The ID is specified using
> conventional semantics: If it begins with 0x, the number
> will be parsed as a hexadecimal (case insensitive) number;
> otherwise, it will be parsed as a decimal number.
> 
> For example, to assign domain 173 (0xad) to the mediated matrix
> device $uuid:
> 
> 	echo 173 > assign_domain
> 
> 	or
> 
> 	echo 0xad > assign_domain
> 
> To unassign domain 173 (0xad):
> 
> 	echo 173 > unassign_domain
> 
> 	or
> 
> 	echo 0xad > unassign_domain
> 
> The assignment will be rejected:
> 
> * If the domain ID exceeds the maximum value for an AP domain:
> 
>   * If the AP Extended Addressing (APXA) facility is installed,
>     the max value is 255
> 
>   * Else the max value is 15
> 
> * If no AP adapters have yet been assigned and there are
>   no AP queues reserved by the VFIO AP driver that have an APQN
>   with an APQI matching that of the AP domain number being
>   assigned.
> 
> * If any of the APQNs that can be derived from the intersection
>   of the APQI being assigned and the AP adapter ID (APID) of
>   each of the AP adapters previously assigned can not be matched
>   with an APQN of an AP queue device reserved by the VFIO AP
>   driver.
> 
> Signed-off-by: Tony Krowiak <akrowiak@linux.vnet.ibm.com>
> ---
>  arch/s390/include/asm/kvm-ap.h    |    1 +
>  drivers/s390/crypto/vfio_ap_ops.c |  215 ++++++++++++++++++++++++++++++++++++-
>  2 files changed, 215 insertions(+), 1 deletions(-)
> 

> diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
> index 90512a6..c448835 100644
> --- a/drivers/s390/crypto/vfio_ap_ops.c
> +++ b/drivers/s390/crypto/vfio_ap_ops.c
> @@ -377,10 +377,223 @@ static ssize_t unassign_adapter_store(struct device *dev,
>  }
>  DEVICE_ATTR_WO(unassign_adapter);
>  
> +/**
> + * vfio_ap_validate_queues_for_apqi
> + *
> + * @ap_matrix: the matrix device
> + * @matrix_mdev: the mediated matrix device
> + * @apqi: an AP queue index (APQI) - corresponds to a domain ID
> + *
> + * Verifies that each APQN that is derived from the intersection of @apqi and
> + * each AP adapter ID (APID) corresponding to an AP domain assigned to the
> + * @matrix_mdev matches the APQN of an AP queue reserved by the VFIO AP device
> + * driver.
> + *
> + * Returns 0 if validation succeeds; otherwise, returns an error.
> + */
> +static int vfio_ap_validate_queues_for_apqi(struct ap_matrix *ap_matrix,
> +					    struct ap_matrix_mdev *matrix_mdev,
> +					    unsigned long apqi)
> +{
> +	int ret;
> +	struct vfio_ap_qid_match qid_match;
> +	unsigned long apid;
> +	struct device_driver *drv = ap_matrix->device.driver;
> +
> +	/**
> +	 * Examine each APQN with the specified APQI
> +	 */
> +	for_each_set_bit_inv(apid, matrix_mdev->matrix->apm,
> +			     matrix_mdev->matrix->apm_max) {
> +		qid_match.qid = AP_MKQID(apid, apqi);
> +		qid_match.dev = NULL;
> +
> +		ret = driver_for_each_device(drv, NULL, &qid_match,
> +					     vfio_ap_queue_match);
> +		if (ret)
> +			return ret;

Hm, I'm wondering whether jumping out of the outer loop is the correct
thing to do here - and if yes, whether we should log an error?

> +
> +		/*
> +		 * If the APQN identifies an AP queue that is reserved by the
> +		 * VFIO AP device driver, continue processing.
> +		 */
> +		if (qid_match.dev)
> +			continue;
> +
> +		pr_err("%s: AP queue %02lx.%04lx not reserved by %s driver",
> +		       VFIO_AP_MATRIX_MODULE_NAME, apqi, apqi,
> +		       VFIO_AP_DRV_NAME);
> +
> +		return -ENXIO;
> +	}
> +
> +	return 0;
> +}