linux-kernel - Re: [PATCH v10 07/16] s390/vfio-ap: sysfs attribute to display the guest's matrix

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Date:   Tue, 29 Sep 2020 17:00:05 -0400
From:   Tony Krowiak <akrowiak@...ux.ibm.com>
To:     Halil Pasic <pasic@...ux.ibm.com>
Cc:     Cornelia Huck <cohuck@...hat.com>, linux-s390@...r.kernel.org,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        freude@...ux.ibm.com, borntraeger@...ibm.com,
        mjrosato@...ux.ibm.com, alex.williamson@...hat.com,
        kwankhede@...dia.com, fiuczy@...ux.ibm.com, frankja@...ux.ibm.com,
        david@...hat.com, imbrenda@...ux.ibm.com, hca@...ux.ibm.com,
        gor@...ux.ibm.com
Subject: Re: [PATCH v10 07/16] s390/vfio-ap: sysfs attribute to display the
 guest's matrix



On 9/26/20 3:16 AM, Halil Pasic wrote:
> On Fri, 18 Sep 2020 13:09:25 -0400
> Tony Krowiak <akrowiak@...ux.ibm.com> wrote:
>
>>
>> On 9/17/20 10:34 AM, Cornelia Huck wrote:
>>> On Fri, 21 Aug 2020 15:56:07 -0400
>>> Tony Krowiak <akrowiak@...ux.ibm.com> wrote:
>>>
>>>> The matrix of adapters and domains configured in a guest's CRYCB may
>>>> differ from the matrix of adapters and domains assigned to the matrix mdev,
>>>> so this patch introduces a sysfs attribute to display the matrix of a guest
>>>> using the matrix mdev. For a matrix mdev denoted by $uuid, the crycb for a
>>>> guest using the matrix mdev can be displayed as follows:
>>>>
>>>>      cat /sys/devices/vfio_ap/matrix/$uuid/guest_matrix
>>>>
>>>> If a guest is not using the matrix mdev at the time the crycb is displayed,
>>>> an error (ENODEV) will be returned.
>>>>
>>>> Signed-off-by: Tony Krowiak <akrowiak@...ux.ibm.com>
>>>> ---
>>>>    drivers/s390/crypto/vfio_ap_ops.c | 58 +++++++++++++++++++++++++++++++
>>>>    1 file changed, 58 insertions(+)
>>>>
>>>> diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
>>>> index efb229033f9e..30bf23734af6 100644
>>>> --- a/drivers/s390/crypto/vfio_ap_ops.c
>>>> +++ b/drivers/s390/crypto/vfio_ap_ops.c
>>>> @@ -1119,6 +1119,63 @@ static ssize_t matrix_show(struct device *dev, struct device_attribute *attr,
>>>>    }
>>>>    static DEVICE_ATTR_RO(matrix);
>>>>    
>>>> +static ssize_t guest_matrix_show(struct device *dev,
>>>> +				 struct device_attribute *attr, char *buf)
>>>> +{
>>>> +	struct mdev_device *mdev = mdev_from_dev(dev);
>>>> +	struct ap_matrix_mdev *matrix_mdev = mdev_get_drvdata(mdev);
>>>> +	char *bufpos = buf;
>>>> +	unsigned long apid;
>>>> +	unsigned long apqi;
>>>> +	unsigned long apid1;
>>>> +	unsigned long apqi1;
>>>> +	unsigned long napm_bits = matrix_mdev->shadow_apcb.apm_max + 1;
>>>> +	unsigned long naqm_bits = matrix_mdev->shadow_apcb.aqm_max + 1;
>>>> +	int nchars = 0;
>>>> +	int n;
>>>> +
>>>> +	if (!vfio_ap_mdev_has_crycb(matrix_mdev))
>>>> +		return -ENODEV;
>>>> +
>>>> +	apid1 = find_first_bit_inv(matrix_mdev->shadow_apcb.apm, napm_bits);
>>>> +	apqi1 = find_first_bit_inv(matrix_mdev->shadow_apcb.aqm, naqm_bits);
>>>> +
>>>> +	mutex_lock(&matrix_dev->lock);
>>>> +
>>>> +	if ((apid1 < napm_bits) && (apqi1 < naqm_bits)) {
>>>> +		for_each_set_bit_inv(apid, matrix_mdev->shadow_apcb.apm,
>>>> +				     napm_bits) {
>>>> +			for_each_set_bit_inv(apqi,
>>>> +					     matrix_mdev->shadow_apcb.aqm,
>>>> +					     naqm_bits) {
>>>> +				n = sprintf(bufpos, "%02lx.%04lx\n", apid,
>>>> +					    apqi);
>>>> +				bufpos += n;
>>>> +				nchars += n;
>>>> +			}
>>>> +		}
>>>> +	} else if (apid1 < napm_bits) {
>>>> +		for_each_set_bit_inv(apid, matrix_mdev->shadow_apcb.apm,
>>>> +				     napm_bits) {
>>>> +			n = sprintf(bufpos, "%02lx.\n", apid);
>>>> +			bufpos += n;
>>>> +			nchars += n;
>>>> +		}
>>>> +	} else if (apqi1 < naqm_bits) {
>>>> +		for_each_set_bit_inv(apqi, matrix_mdev->shadow_apcb.aqm,
>>>> +				     naqm_bits) {
>>>> +			n = sprintf(bufpos, ".%04lx\n", apqi);
>>>> +			bufpos += n;
>>>> +			nchars += n;
>>>> +		}
>>>> +	}
>>>> +
>>>> +	mutex_unlock(&matrix_dev->lock);
>>>> +
>>>> +	return nchars;
>>>> +}
>>> This basically looks like a version of matrix_show() operating on the
>>> shadow apcb. I'm wondering if we could consolidate these two functions
>>> by passing in the structure to operate on as a parameter? Might not be
>>> worth the effort, though.
>> We still need the two functions because they back the mdev's
>> sysfs matrix and guest_matrix attributes, but we could call a function.
>> I'm not sure it buys us much though.
> The logic seems identical with the exception that the guest variant
> checks if vfio_ap_mdev_has_crycb(matrix_mdev). I'm not a big fan of
> duplicated code, and especially not in such close proximity. I'm voting
> for factoring out the common logic.

Not a problem, will do.

>
> Otherwise looks OK.
>
> Regards,
> Halil
>