Re: [PATCH v9 10/22] s390: vfio-ap: sysfs interfaces to configure adapters

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On 08/15/2018 05:52 AM, Cornelia Huck wrote:
On Mon, 13 Aug 2018 17:48:07 -0400
Tony Krowiak <akrowiak@xxxxxxxxxxxxxxxxxx> wrote:

+/**
+ * assign_adapter_store
+ *
+ * @dev: the matrix device
+ * @attr: a mediated matrix device attribute
+ * @buf: a buffer containing the adapter ID (APID) to be assigned
+ * @count: the number of bytes in @buf
+ *
+ * Parses the APID from @buf and assigns it to the mediated matrix device.
+ *
+ * Returns the number of bytes processed if the APID is valid; otherwise returns
+ * an error.
+ */
+static ssize_t assign_adapter_store(struct device *dev,
+				    struct device_attribute *attr,
+				    const char *buf, size_t count)
+{
+	int ret = 0;
You don't need to initialize this to 0, as kstrtoul will set it in any
case.

Right you are! Will change it.


+	unsigned long apid;
+	struct mdev_device *mdev = mdev_from_dev(dev);
+	struct ap_matrix_mdev *matrix_mdev = mdev_get_drvdata(mdev);
+	unsigned long max_apid = matrix_mdev->matrix.apm_max;
+
+	ret = kstrtoul(buf, 0, &apid);
+	if (ret)
+		return ret;
+	if (apid > max_apid)
+		return -EINVAL;
+
+	/* Set the bit in the AP mask (APM) corresponding to the AP adapter
+	 * number (APID). The bits in the mask, from most significant to least
+	 * significant bit, correspond to APIDs 0-255.
+	 */
+	mutex_lock(&matrix_dev.lock);
+
+	ret = vfio_ap_mdev_verify_queues_reserved_for_apid(matrix_mdev, apid);
That function name really is a mouthful :) I don't have any better
suggestions, though.

It is, but I think it describes exactly what the function does.


+	if (ret)
+		goto done;
+
+	set_bit_inv(apid, matrix_mdev->matrix.apm);
+
+	ret = vfio_ap_mdev_verify_no_sharing(matrix_mdev);
+	if (ret)
+		goto share_err;
+
+	ret = count;
+	goto done;
+
+share_err:
+	clear_bit_inv(apid, matrix_mdev->matrix.apm);
+done:
+	mutex_unlock(&matrix_dev.lock);
+
+	return ret;
+}
+static DEVICE_ATTR_WO(assign_adapter);
+
+/**
+ * unassign_adapter_store
+ *
+ * @dev: the matrix device
+ * @attr: a mediated matrix device attribute
+ * @buf: a buffer containing the adapter ID (APID) to be assigned
+ * @count: the number of bytes in @buf
+ *
+ * Parses the APID from @buf and unassigns it from the mediated matrix device.
+ * The APID must be a valid value
A valid value, but not necessarily assigned, right?

You are correct, if the APID is not assigned, then the corresponding bit will be cleared regardless. In a previous version, the functions failed if the APID is not assigned, but a colleague removed that check. I guess it makes sense given it really does not hurt anything to ask to unassign an APID that isn't assigned to begin with. Would you prefer I update the comment, or do you feel the user
should be made aware of an attempt to unassign an APID that is not assigned?


+ *
+ * Returns the number of bytes processed if the APID is valid; otherwise returns
+ * an error.
+ */
+static ssize_t unassign_adapter_store(struct device *dev,
+				      struct device_attribute *attr,
+				      const char *buf, size_t count)
+{
+	int ret;
+	unsigned long apid;
+	struct mdev_device *mdev = mdev_from_dev(dev);
+	struct ap_matrix_mdev *matrix_mdev = mdev_get_drvdata(mdev);
+
+	ret = kstrtoul(buf, 0, &apid);
+	if (ret)
+		return ret;
+
+	if (apid > matrix_mdev->matrix.apm_max)
+		return -EINVAL;
+
+	mutex_lock(&matrix_dev.lock);
+	clear_bit_inv((unsigned long)apid, matrix_mdev->matrix.apm);
+	mutex_unlock(&matrix_dev.lock);
+
+	return count;
+}
+DEVICE_ATTR_WO(unassign_adapter);
In general, looks good to me.

That is good news indeed.






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