PCI: Add dev_flags bit to access VPD through function 0

Add a dev_flags bit, PCI_DEV_FLAGS_VPD_REF_F0, to access VPD through
function 0 to provide VPD access on other functions.  This is for hardware
devices that provide copies of the same VPD capability registers in
multiple functions.  Because the kernel expects that each function has its
own registers, both the locking and the state tracking are affected by VPD
accesses to different functions.

On such devices for example, if a VPD write is performed on function 0,
*any* later attempt to read VPD from any other function of that device will
hang.  This has to do with how the kernel tracks the expected value of the
F bit per function.

Concurrent accesses to different functions of the same device can not only
hang but also corrupt both read and write VPD data.

When hangs occur, typically the error message:

  vpd r/w failed.  This is likely a firmware bug on this device.

will be seen.

Never set this bit on function 0 or there will be an infinite recursion.

Signed-off-by: Mark Rustad <mark.d.rustad@intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Alexander Duyck <alexander.h.duyck@redhat.com>
CC: stable@vger.kernel.org

1 files changed, 2 insertions, 0 deletions

diff --git a/include/linux/pci.h b/include/linux/pci.h
index 8a0321a8fb59..8edb125db13a 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -180,6 +180,8 @@ enum pci_dev_flags {
 	PCI_DEV_FLAGS_NO_BUS_RESET = (__force pci_dev_flags_t) (1 << 6),
 	/* Do not use PM reset even if device advertises NoSoftRst- */
 	PCI_DEV_FLAGS_NO_PM_RESET = (__force pci_dev_flags_t) (1 << 7),
+	/* Get VPD from function 0 VPD */
+	PCI_DEV_FLAGS_VPD_REF_F0 = (__force pci_dev_flags_t) (1 << 8),
 };
 
 enum pci_irq_reroute_variant {