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

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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.






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