diff options
Diffstat (limited to 'PCI-aspm-deal-with-missing-root-ports-in-link-state-handling.patch')
| -rw-r--r-- | PCI-aspm-deal-with-missing-root-ports-in-link-state-handling.patch | 55 |
1 files changed, 55 insertions, 0 deletions
diff --git a/PCI-aspm-deal-with-missing-root-ports-in-link-state-handling.patch b/PCI-aspm-deal-with-missing-root-ports-in-link-state-handling.patch new file mode 100644 index 000000000..03b011561 --- /dev/null +++ b/PCI-aspm-deal-with-missing-root-ports-in-link-state-handling.patch @@ -0,0 +1,55 @@ +From patchwork Mon Oct 2 14:08:40 2017 +Content-Type: text/plain; charset="utf-8" +MIME-Version: 1.0 +Content-Transfer-Encoding: 7bit +Subject: PCI: aspm: deal with missing root ports in link state handling +From: Ard Biesheuvel <ard.biesheuvel@linaro.org> +X-Patchwork-Id: 9980861 +Message-Id: <20171002140840.7767-1-ard.biesheuvel@linaro.org> +To: linux-pci@vger.kernel.org, bhelgaas@google.com +Cc: graeme.gregory@linaro.org, leif.lindholm@linaro.org, + daniel.thompson@Linaro.org, Ard Biesheuvel <ard.biesheuvel@linaro.org> +Date: Mon, 2 Oct 2017 15:08:40 +0100 + +Even though it is unconventional, some PCIe host implementations omit +the root ports entirely, and simply consist of a host bridge (which +is not modeled as a device in the PCI hierarchy) and a link. + +When the downstream device is an endpoint, our current code does not +seem to mind this unusual configuration. However, when PCIe switches +are involved, the ASPM code assumes that any downstream switch port +has a parent, and blindly derefences the bus->parent->self field of +the pci_dev struct to chain the downstream link state to the link +state of the root port. Given that the root port is missing, the link +is not modeled at all, and nor is the link state, and attempting to +access it results in a NULL pointer dereference and a crash. + +So let's avoid this by allowing the link state chain to terminate at +the downstream port if no root port exists. + +Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> +--- + drivers/pci/pcie/aspm.c | 8 ++++++-- + 1 file changed, 6 insertions(+), 2 deletions(-) + +diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c +index 1dfa10cc566b..0bea8498b5a5 100644 +--- a/drivers/pci/pcie/aspm.c ++++ b/drivers/pci/pcie/aspm.c +@@ -802,10 +802,14 @@ static struct pcie_link_state *alloc_pcie_link_state(struct pci_dev *pdev) + + /* + * Root Ports and PCI/PCI-X to PCIe Bridges are roots of PCIe +- * hierarchies. ++ * hierarchies. Note that some PCIe host implementations omit ++ * the root ports entirely, in which case a downstream port on ++ * a switch may become the root of the link state chain for all ++ * its subordinate endpoints. + */ + if (pci_pcie_type(pdev) == PCI_EXP_TYPE_ROOT_PORT || +- pci_pcie_type(pdev) == PCI_EXP_TYPE_PCIE_BRIDGE) { ++ pci_pcie_type(pdev) == PCI_EXP_TYPE_PCIE_BRIDGE || ++ !pdev->bus->parent->self) { + link->root = link; + } else { + struct pcie_link_state *parent; |