diff mbox

[PATCHv5,3/5] pci: No config access for disconnected devices

Message ID 1486144555-5526-4-git-send-email-keith.busch@intel.com (mailing list archive)
State New, archived
Delegated to: Bjorn Helgaas
Headers show

Commit Message

Keith Busch Feb. 3, 2017, 5:55 p.m. UTC 
If we've  detected the PCI device is disconnected, there is no need to
attempt to access its config space since we know the operation will
fail. This patch has all the config reads and writes return -ENODEV
error immediately when in such a state.

If a config read is sent to a disconnected device, the value will be
set to all 1's. This is the same as what hardware is expected to return
when accessing a removed device, but software can do this faster without
relying on hardware.

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

Comments

Christoph Hellwig Feb. 6, 2017, 5:34 p.m. UTC | #1 
Looks fine:

Reviewed-by: Christoph Hellwig <hch@lst.de>

Although a comment in the code explaining why return both an error
and set the returned value to all bits set might be helpful for
future readers of the code.
diff mbox

Patch

diff --git a/drivers/pci/access.c b/drivers/pci/access.c
index d37b2ed..d63e9dd 100644
--- a/drivers/pci/access.c
+++ b/drivers/pci/access.c
@@ -892,12 +892,20 @@  EXPORT_SYMBOL(pcie_capability_clear_and_set_dword);
 
 int pci_read_config_byte(const struct pci_dev *dev, int where, u8 *val)
 {
+	if (pci_dev_is_disconnected(dev)) {
+		*val = ~0;
+		return -ENODEV;
+	}
 	return pci_bus_read_config_byte(dev->bus, dev->devfn, where, val);
 }
 EXPORT_SYMBOL(pci_read_config_byte);
 
 int pci_read_config_word(const struct pci_dev *dev, int where, u16 *val)
 {
+	if (pci_dev_is_disconnected(dev)) {
+		*val = ~0;
+		return -ENODEV;
+	}
 	return pci_bus_read_config_word(dev->bus, dev->devfn, where, val);
 }
 EXPORT_SYMBOL(pci_read_config_word);
@@ -905,18 +913,26 @@  EXPORT_SYMBOL(pci_read_config_word);
 int pci_read_config_dword(const struct pci_dev *dev, int where,
 					u32 *val)
 {
+	if (pci_dev_is_disconnected(dev)) {
+		*val = ~0;
+		return -ENODEV;
+	}
 	return pci_bus_read_config_dword(dev->bus, dev->devfn, where, val);
 }
 EXPORT_SYMBOL(pci_read_config_dword);
 
 int pci_write_config_byte(const struct pci_dev *dev, int where, u8 val)
 {
+	if (pci_dev_is_disconnected(dev))
+		return -ENODEV;
 	return pci_bus_write_config_byte(dev->bus, dev->devfn, where, val);
 }
 EXPORT_SYMBOL(pci_write_config_byte);
 
 int pci_write_config_word(const struct pci_dev *dev, int where, u16 val)
 {
+	if (pci_dev_is_disconnected(dev))
+		return -ENODEV;
 	return pci_bus_write_config_word(dev->bus, dev->devfn, where, val);
 }
 EXPORT_SYMBOL(pci_write_config_word);
@@ -924,6 +940,8 @@  EXPORT_SYMBOL(pci_write_config_word);
 int pci_write_config_dword(const struct pci_dev *dev, int where,
 					 u32 val)
 {
+	if (pci_dev_is_disconnected(dev))
+		return -ENODEV;
 	return pci_bus_write_config_dword(dev->bus, dev->devfn, where, val);
 }
 EXPORT_SYMBOL(pci_write_config_dword);