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PCI: Don't attempt config access to disconnected devices 

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.
Make all the config reads and writes return -ENODEV error immediately when
in such a state.

If a caller requests a config read to a disconnected device, return a data
value of 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.

Tested-by: Krishna Dhulipala <krishnad@fb.com>
Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Wei Zhang <wzhang@fb.com>
This commit is contained in:
Keith Busch 2017-03-29 22:49:06 -05:00 committed by Bjorn Helgaas
parent 89ee9f7680
commit 4b10388347
1 changed files with 18 additions and 0 deletions
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18
drivers/pci/access.c
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@ -893,12 +893,20 @@ 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);
@ -906,18 +914,26 @@ 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);
@ -925,6 +941,8 @@ 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);