PCI: Skip MPS logic for Virtual Functions (VFs)

BugLink: https://bugs.launchpad.net/bugs/1835845
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>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 6ba8174fab03009d1528e9885c34b95ce78ff96f..d1b30d5df6b53cec84d5fef3204f78764719108e 100644 (file)
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -1616,6 +1616,10 @@ 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);