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Commit 5895af79 authored by Yijing Wang's avatar Yijing Wang Committed by Bjorn Helgaas
Browse files

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: default avatarJoe Jin <joe.jin@oracle.com>
Signed-off-by: default avatarYijing Wang <wangyijing@huawei.com>
Signed-off-by: default avatarBjorn Helgaas <bhelgaas@google.com>
Cc: Jon Mason <jdmason@kudzu.us>
parent 3315472c

drivers/pci/probe.c

+21 −3
Original line number Diff line number Diff line
@@ -1582,6 +1582,22 @@ static void pcie_write_mrrs(struct pci_dev *dev) 
			"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 @@ static int pcie_bus_configure_set(struct pci_dev *dev, void *data) 
	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 @@ void pcie_bus_configure_settings(struct pci_bus *bus) 
	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.