[PATCH 4.18 17/22] PCI: Skip MPS logic for Virtual Functions (VFs)

From: Greg Kroah-Hartman
Date: Thu Aug 23 2018 - 05:11:11 EST

4.18-stable review patch. If anyone has any objections, please let me know.


From: Myron Stowe <myron.stowe@xxxxxxxxxx>

commit 3dbe97efe8bf450b183d6dee2305cbc032e6b8a4 upstream.

PCIe r4.0, sec, "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 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

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@xxxxxxxxxx>
Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx # 4.3+
Cc: Keith Busch <keith.busch@xxxxxxxxx>
Cc: Sinan Kaya <okaya@xxxxxxxxxx>
Cc: Dongdong Liu <liudongdong3@xxxxxxxxxx>
Cc: Jon Mason <jdmason@xxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

drivers/pci/probe.c | 4 ++++
1 file changed, 4 insertions(+)

--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -1730,6 +1730,10 @@ static void pci_configure_mps(struct pci
if (!pci_is_pcie(dev) || !bridge || !pci_is_pcie(bridge))

+ /* 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);