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

[Tony Krowiak]

On 9/17/20 10:34 AM, Cornelia Huck wrote:
> On Fri, 21 Aug 2020 15:56:07 -0400
> Tony Krowiak <akrowiak@xxxxxxxxxxxxx> 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@xxxxxxxxxxxxx>
> > ---
> >   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.

>