iommu/vt-d: Report domain usage in sysfs

Debugging domain ID leakage typically requires long running tests in
order to exhaust the domain ID space or kernel instrumentation to
track the setting and clearing of bits.  A couple trivial intel-iommu
specific sysfs extensions make it much easier to expose the IOMMU
capabilities and current usage.
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/intel-iommu.c

@@ -4449,11 +4449,32 @@ static ssize_t intel_iommu_show_ecap(struct device *dev,
 }
 static DEVICE_ATTR(ecap, S_IRUGO, intel_iommu_show_ecap, NULL);
 
+static ssize_t intel_iommu_show_ndoms(struct device *dev,
+				      struct device_attribute *attr,
+				      char *buf)
+{
+	struct intel_iommu *iommu = dev_get_drvdata(dev);
+	return sprintf(buf, "%ld\n", cap_ndoms(iommu->cap));
+}
+static DEVICE_ATTR(domains_supported, S_IRUGO, intel_iommu_show_ndoms, NULL);
+
+static ssize_t intel_iommu_show_ndoms_used(struct device *dev,
+					   struct device_attribute *attr,
+					   char *buf)
+{
+	struct intel_iommu *iommu = dev_get_drvdata(dev);
+	return sprintf(buf, "%d\n", bitmap_weight(iommu->domain_ids,
+						  cap_ndoms(iommu->cap)));
+}
+static DEVICE_ATTR(domains_used, S_IRUGO, intel_iommu_show_ndoms_used, NULL);
+
 static struct attribute *intel_iommu_attrs[] = {
 	&dev_attr_version.attr,
 	&dev_attr_address.attr,
 	&dev_attr_cap.attr,
 	&dev_attr_ecap.attr,
+	&dev_attr_domains_supported.attr,
+	&dev_attr_domains_used.attr,
 	NULL,
 };