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>
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@ -1582,6 +1582,22 @@ static void pcie_write_mrrs(struct pci_dev *dev)
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"with pci=pcie_bus_safe.\n");
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}
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static void pcie_bus_detect_mps(struct pci_dev *dev)
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{
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struct pci_dev *bridge = dev->bus->self;
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int mps, p_mps;
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if (!bridge)
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return;
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mps = pcie_get_mps(dev);
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p_mps = pcie_get_mps(bridge);
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if (mps != p_mps)
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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",
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mps, pci_name(bridge), p_mps);
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}
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static int pcie_bus_configure_set(struct pci_dev *dev, void *data)
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{
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int mps, orig_mps;
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@ -1589,6 +1605,11 @@ static int pcie_bus_configure_set(struct pci_dev *dev, void *data)
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if (!pci_is_pcie(dev))
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return 0;
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if (pcie_bus_config == PCIE_BUS_TUNE_OFF) {
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pcie_bus_detect_mps(dev);
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return 0;
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}
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mps = 128 << *(u8 *)data;
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orig_mps = pcie_get_mps(dev);
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@ -1616,9 +1637,6 @@ void pcie_bus_configure_settings(struct pci_bus *bus)
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if (!pci_is_pcie(bus->self))
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return;
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if (pcie_bus_config == PCIE_BUS_TUNE_OFF)
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return;
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/* FIXME - Peer to peer DMA is possible, though the endpoint would need
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* to be aware of the MPS of the destination. To work around this,
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* simply force the MPS of the entire system to the smallest possible.
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