• Mark Rustad's avatar
    PCI: Add dev_flags bit to access VPD through function 0 · 932c435c
    Mark Rustad authored
    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: 's avatarMark Rustad <mark.d.rustad@intel.com>
    Signed-off-by: 's avatarBjorn Helgaas <bhelgaas@google.com>
    Acked-by: 's avatarAlexander Duyck <alexander.h.duyck@redhat.com>
    CC: stable@vger.kernel.org
    932c435c
access.c 18.5 KB