PCI: Skip MPS logic for Virtual Functions (VFs)

commit 3dbe97efe8bf450b183d6dee2305cbc032e6b8a4 upstream.

PCIe r4.0, sec 9.3.5.4, "Device Control Register", shows both
Max_Payload_Size (MPS) and Max_Read_request_Size (MRRS) to be 'RsvdP' for
VFs.  Just prior to the table it states:

  "PF and VF functionality is defined in Section 7.5.3.4 except where
   noted in Table 9-16.  For VF fields marked 'RsvdP', the PF setting
   applies to the VF."

All of which implies that with respect to Max_Payload_Size Supported
(MPSS), MPS, and MRRS values, we should not be paying any attention to the
VF's fields, but rather only to the PF's.  Only looking at the PF's fields
also logically makes sense as it's the sole physical interface to the PCIe
bus.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=200527
Fixes: 27d868b5e6cf ("PCI: Set MPS to match upstream bridge")
Signed-off-by: Myron Stowe <myron.stowe@redhat.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: stable@vger.kernel.org # 4.3+
Cc: Keith Busch <keith.busch@intel.com>
Cc: Sinan Kaya <okaya@kernel.org>
Cc: Dongdong Liu <liudongdong3@huawei.com>
Cc: Jon Mason <jdmason@kudzu.us>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 85637529bc3a833e0889a2a1a533b8f547eda90f..31d416eeb7878282d9ae0e345da5ac2e7793d75e 100644 (file)
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -1338,6 +1338,10 @@ static void pci_configure_mps(struct pci_dev *dev)
        if (!pci_is_pcie(dev) || !bridge || !pci_is_pcie(bridge))
                return;
 
+       /* MPS and MRRS fields are of type 'RsvdP' for VFs, short-circuit out */
+       if (dev->is_virtfn)
+               return;
+
        mps = pcie_get_mps(dev);
        p_mps = pcie_get_mps(bridge);