[PATCHv2 2/4] pci: No config access for removed devices

[Keith Busch <keith.busch@intel.com>]

If we've  detected that the PCI device is removed, do not attempt to
access the device's config space.

On a config read, if the device is not present, the value returned will be
set to all 1's. This is the same as what hardware would normally return
when accessing a removed device, but we do not need to repeatedly test
hardware's completion capabilities if software can take a short-cut.

Signed-off-by: Keith Busch <keith.busch@intel.com>
---
 include/linux/pci.h | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/include/linux/pci.h b/include/linux/pci.h
index 865d3ec..1b62f7a 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -932,28 +932,46 @@ struct pci_ops *pci_bus_set_ops(struct pci_bus *bus, struct pci_ops *ops);
 
 static inline int pci_read_config_byte(const struct pci_dev *dev, int where, u8 *val)
 {
+	if (unlikely(dev->is_removed)) {
+		*val = ~0;
+		return -ENODEV;
+	}
 	return pci_bus_read_config_byte(dev->bus, dev->devfn, where, val);
 }
 static inline int pci_read_config_word(const struct pci_dev *dev, int where, u16 *val)
 {
+	if (unlikely(dev->is_removed)) {
+		*val = ~0;
+		return -ENODEV;
+	}
 	return pci_bus_read_config_word(dev->bus, dev->devfn, where, val);
 }
 static inline int pci_read_config_dword(const struct pci_dev *dev, int where,
 					u32 *val)
 {
+	if (unlikely(dev->is_removed)) {
+		*val = ~0;
+		return -ENODEV;
+	}
 	return pci_bus_read_config_dword(dev->bus, dev->devfn, where, val);
 }
 static inline int pci_write_config_byte(const struct pci_dev *dev, int where, u8 val)
 {
+	if (unlikely(dev->is_removed))
+		return -ENODEV;
 	return pci_bus_write_config_byte(dev->bus, dev->devfn, where, val);
 }
 static inline int pci_write_config_word(const struct pci_dev *dev, int where, u16 val)
 {
+	if (unlikely(dev->is_removed))
+		return -ENODEV;
 	return pci_bus_write_config_word(dev->bus, dev->devfn, where, val);
 }
 static inline int pci_write_config_dword(const struct pci_dev *dev, int where,
 					 u32 val)
 {
+	if (unlikely(dev->is_removed))
+		return -ENODEV;
 	return pci_bus_write_config_dword(dev->bus, dev->devfn, where, val);
 }
 
-- 
2.7.2