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

Halil Pasic
2020-09-26T07:16:20Z

On Fri, 18 Sep 2020 13:09:25 -0400
Tony Krowiak <akrowiak@linux.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@linux.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@linux.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.

Otherwise looks OK.

Regards,
Halil