PCI: SRIOV control and status via sysfs

Provide files under sysfs to determine the maximum number of VFs
an SR-IOV-capable PCIe device supports, and methods to enable and
disable the VFs on a per-device basis.

Currently, VF enablement by SR-IOV-capable PCIe devices is done
via driver-specific module parameters.  If not setup in modprobe files,
it requires admin to unload & reload PF drivers with number of desired
VFs to enable.  Additionally, the enablement is system wide: all
devices controlled by the same driver have the same number of VFs
enabled.  Although the latter is probably desired, there are PCI
configurations setup by system BIOS that may not enable that to occur.

Two files are created for the PF of PCIe devices with SR-IOV support:

    sriov_totalvfs	Contains the maximum number of VFs the device
			could support as reported by the TotalVFs register
			in the SR-IOV extended capability.

    sriov_numvfs	Contains the number of VFs currently enabled on
			this device as reported by the NumVFs register in
			the SR-IOV extended capability.

			Writing zero to this file disables all VFs.

			Writing a positive number to this file enables that
			number of VFs.

These files are readable for all SR-IOV PF devices.  Writes to the
sriov_numvfs file are effective only if a driver that supports the
sriov_configure() method is attached.

Signed-off-by: Donald Dutile <ddutile@redhat.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

drivers/pci/pci-sysfs.c

@@ -404,6 +404,106 @@ static ssize_t d3cold_allowed_show(struct device *dev,
 }
 #endif
 
+#ifdef CONFIG_PCI_IOV
+static ssize_t sriov_totalvfs_show(struct device *dev,
+				   struct device_attribute *attr,
+				   char *buf)
+{
+	struct pci_dev *pdev = to_pci_dev(dev);
+
+	return sprintf(buf, "%u\n", pdev->sriov->total);
+}
+
+
+static ssize_t sriov_numvfs_show(struct device *dev,
+				 struct device_attribute *attr,
+				 char *buf)
+{
+	struct pci_dev *pdev = to_pci_dev(dev);
+
+	return sprintf(buf, "%u\n", pdev->sriov->nr_virtfn);
+}
+
+/*
+ * num_vfs > 0; number of vfs to enable
+ * num_vfs = 0; disable all vfs
+ *
+ * Note: SRIOV spec doesn't allow partial VF
+ *       disable, so its all or none.
+ */
+static ssize_t sriov_numvfs_store(struct device *dev,
+				  struct device_attribute *attr,
+				  const char *buf, size_t count)
+{
+	struct pci_dev *pdev = to_pci_dev(dev);
+	int num_vfs_enabled = 0;
+	int num_vfs;
+	int ret = 0;
+	u16 total;
+
+	if (kstrtoint(buf, 0, &num_vfs) < 0)
+		return -EINVAL;
+
+	/* is PF driver loaded w/callback */
+	if (!pdev->driver || !pdev->driver->sriov_configure) {
+		dev_info(&pdev->dev,
+			 "Driver doesn't support SRIOV configuration via sysfs\n");
+		return -ENOSYS;
+	}
+
+	/* if enabling vf's ... */
+	total = pdev->sriov->total;
+	/* Requested VFs to enable < totalvfs and none enabled already */
+	if ((num_vfs > 0) && (num_vfs <= total)) {
+		if (pdev->sriov->nr_virtfn == 0) {
+			num_vfs_enabled =
+				pdev->driver->sriov_configure(pdev, num_vfs);
+			if ((num_vfs_enabled >= 0) &&
+			    (num_vfs_enabled != num_vfs)) {
+				dev_warn(&pdev->dev,
+					 "Only %d VFs enabled\n",
+					 num_vfs_enabled);
+				return count;
+			} else if (num_vfs_enabled < 0)
+				/* error code from driver callback */
+				return num_vfs_enabled;
+		} else if (num_vfs == pdev->sriov->nr_virtfn) {
+			dev_warn(&pdev->dev,
+				 "%d VFs already enabled; no enable action taken\n",
+				 num_vfs);
+			return count;
+		} else {
+			dev_warn(&pdev->dev,
+				 "%d VFs already enabled. Disable before enabling %d VFs\n",
+				 pdev->sriov->nr_virtfn, num_vfs);
+			return -EINVAL;
+		}
+	}
+
+	/* disable vfs */
+	if (num_vfs == 0) {
+		if (pdev->sriov->nr_virtfn != 0) {
+			ret = pdev->driver->sriov_configure(pdev, 0);
+			return ret ? ret : count;
+		} else {
+			dev_warn(&pdev->dev,
+				 "All VFs disabled; no disable action taken\n");
+			return count;
+		}
+	}
+
+	dev_err(&pdev->dev,
+		"Invalid value for number of VFs to enable: %d\n", num_vfs);
+
+	return -EINVAL;
+}
+
+static struct device_attribute sriov_totalvfs_attr = __ATTR_RO(sriov_totalvfs);
+static struct device_attribute sriov_numvfs_attr =
+		__ATTR(sriov_numvfs, (S_IRUGO|S_IWUSR|S_IWGRP),
+		       sriov_numvfs_show, sriov_numvfs_store);
+#endif /* CONFIG_PCI_IOV */
+
 struct device_attribute pci_dev_attrs[] = {
 	__ATTR_RO(resource),
 	__ATTR_RO(vendor),
@@ -1421,13 +1521,40 @@ static umode_t pci_dev_attrs_are_visible(struct kobject *kobj,
 	return a->mode;
 }
 
+#ifdef CONFIG_PCI_IOV
+static struct attribute *sriov_dev_attrs[] = {
+	&sriov_totalvfs_attr.attr,
+	&sriov_numvfs_attr.attr,
+	NULL,
+};
+
+static umode_t sriov_attrs_are_visible(struct kobject *kobj,
+					 struct attribute *a, int n)
+{
+	struct device *dev = container_of(kobj, struct device, kobj);
+
+	if (!dev_is_pf(dev))
+		return 0;
+
+	return a->mode;
+}
+
+static struct attribute_group sriov_dev_attr_group = {
+	.attrs = sriov_dev_attrs,
+	.is_visible = sriov_attrs_are_visible,
+};
+#endif /* CONFIG_PCI_IOV */
+
 static struct attribute_group pci_dev_attr_group = {
 	.attrs = pci_dev_dev_attrs,
 	.is_visible = pci_dev_attrs_are_visible,
 };
 
 static const struct attribute_group *pci_dev_attr_groups[] = {
 	&pci_dev_attr_group,
+#ifdef CONFIG_PCI_IOV
+	&sriov_dev_attr_group,
+#endif
 	NULL,
 };
 

include/linux/pci.h

@@ -573,6 +573,7 @@ struct pci_driver {
 	int  (*resume_early) (struct pci_dev *dev);
 	int  (*resume) (struct pci_dev *dev);	                /* Device woken up */
 	void (*shutdown) (struct pci_dev *dev);
+	int (*sriov_configure) (struct pci_dev *dev, int num_vfs); /* PF pdev */
 	const struct pci_error_handlers *err_handler;
 	struct device_driver	driver;
 	struct pci_dynids dynids;