PCI: Warn if unsafe MPS settings detected
If a BIOS configures MPS incorrectly, devices may not work normally.
For example, if a bridge has MPS set larger than an endpoint below it,
the endpoint may discard packets.
To help diagnose this issue, print a warning if we find an endpoint
MPS setting different than that of the upstream bridge.
[bhelgaas: changelog, "bridge" temporary, warning text]
Reference: https://bugzilla.kernel.org/show_bug.cgi?id=60799
Reported-by: Joe Jin <joe.jin@oracle.com>
Signed-off-by: Yijing Wang <wangyijing@huawei.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: Jon Mason <jdmason@kudzu.us>
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 94c5a77c..cd5c4ac 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -1582,6 +1582,22 @@
"with pci=pcie_bus_safe.\n");
}
+static void pcie_bus_detect_mps(struct pci_dev *dev)
+{
+ struct pci_dev *bridge = dev->bus->self;
+ int mps, p_mps;
+
+ if (!bridge)
+ return;
+
+ mps = pcie_get_mps(dev);
+ p_mps = pcie_get_mps(bridge);
+
+ if (mps != p_mps)
+ dev_warn(&dev->dev, "Max Payload Size %d, but upstream %s set to %d; if necessary, use \"pci=pcie_bus_safe\" and report a bug\n",
+ mps, pci_name(bridge), p_mps);
+}
+
static int pcie_bus_configure_set(struct pci_dev *dev, void *data)
{
int mps, orig_mps;
@@ -1589,6 +1605,11 @@
if (!pci_is_pcie(dev))
return 0;
+ if (pcie_bus_config == PCIE_BUS_TUNE_OFF) {
+ pcie_bus_detect_mps(dev);
+ return 0;
+ }
+
mps = 128 << *(u8 *)data;
orig_mps = pcie_get_mps(dev);
@@ -1616,9 +1637,6 @@
if (!pci_is_pcie(bus->self))
return;
- if (pcie_bus_config == PCIE_BUS_TUNE_OFF)
- return;
-
/* FIXME - Peer to peer DMA is possible, though the endpoint would need
* to be aware of the MPS of the destination. To work around this,
* simply force the MPS of the entire system to the smallest possible.