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

[Tony Krowiak]

On 9/26/20 3:16 AM, Halil Pasic wrote:
> On Fri, 18 Sep 2020 13:09:25 -0400
> Tony Krowiak <akrowiak@xxxxxxxxxxxxx> wrote:
>
> > 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.
> 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