PCI/VPD: Add runtime power management to sysfs interface

Unlike default access to config space through sysfs, the VPD read and write
functions don't actively manage the runtime power management state of the
device during access.  Since commit 7ab5e10 ("vfio/pci: Move the
unused device into low power state with runtime PM"), the vfio-pci driver
will use runtime power management and release unused devices to make use of
low power states.  Attempting to access VPD information in D3cold can
result in incorrect information or kernel crashes depending on the system
behavior.

Wrap the VPD read/write bin attribute handlers in runtime PM and take into
account the potential quirk to select the correct device to wake.

Link: https://lore.kernel.org/r/20230803171233.3810944-2-alex.williamson@redhat.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
[bhelgaas: tweak pci_dev_put() test to match the pci_get_func0_dev() test]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

Author: awilliam

drivers/pci/vpd.c

@@ -275,17 +275,47 @@ static ssize_t vpd_read(struct file *filp, struct kobject *kobj,
 			size_t count)
 {
 	struct pci_dev *dev = to_pci_dev(kobj_to_dev(kobj));
+	struct pci_dev *vpd_dev = dev;
+	ssize_t ret;
+
+	if (dev->dev_flags & PCI_DEV_FLAGS_VPD_REF_F0) {
+		vpd_dev = pci_get_func0_dev(dev);
+		if (!vpd_dev)
+			return -ENODEV;
+	}
+
+	pci_config_pm_runtime_get(vpd_dev);
+	ret = pci_read_vpd(vpd_dev, off, count, buf);
+	pci_config_pm_runtime_put(vpd_dev);
+
+	if (dev->dev_flags & PCI_DEV_FLAGS_VPD_REF_F0)
+		pci_dev_put(vpd_dev);
 
-	return pci_read_vpd(dev, off, count, buf);
+	return ret;
 }
 
 static ssize_t vpd_write(struct file *filp, struct kobject *kobj,
 			 struct bin_attribute *bin_attr, char *buf, loff_t off,
 			 size_t count)
 {
 	struct pci_dev *dev = to_pci_dev(kobj_to_dev(kobj));
+	struct pci_dev *vpd_dev = dev;
+	ssize_t ret;
+
+	if (dev->dev_flags & PCI_DEV_FLAGS_VPD_REF_F0) {
+		vpd_dev = pci_get_func0_dev(dev);
+		if (!vpd_dev)
+			return -ENODEV;
+	}
+
+	pci_config_pm_runtime_get(vpd_dev);
+	ret = pci_write_vpd(vpd_dev, off, count, buf);
+	pci_config_pm_runtime_put(vpd_dev);
+
+	if (dev->dev_flags & PCI_DEV_FLAGS_VPD_REF_F0)
+		pci_dev_put(vpd_dev);
 
-	return pci_write_vpd(dev, off, count, buf);
+	return ret;
 }
 static BIN_ATTR(vpd, 0600, vpd_read, vpd_write, 0);