4.18-stable review patch. If anyone has any objections, please let me know.
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From: Benjamin Herrenschmidt benh@kernel.crashing.org
commit db2173198b9513f7add8009f225afa1f1c79bcc6 upstream.
The generic code is racy when multiple children of a PCI bridge try to enable it simultaneously.
This leads to drivers trying to access a device through a not-yet-enabled bridge, and this EEH errors under various circumstances when using parallel driver probing.
There is work going on to fix that properly in the PCI core but it will take some time.
x86 gets away with it because (outside of hotplug), the BIOS enables all the bridges at boot time.
This patch does the same thing on powernv by enabling all bridges that have child devices at boot time, thus avoiding subsequent races. It's suitable for backporting to stable and distros, while the proper PCI fix will probably be significantly more invasive.
Signed-off-by: Benjamin Herrenschmidt benh@kernel.crashing.org Cc: stable@vger.kernel.org Signed-off-by: Michael Ellerman mpe@ellerman.id.au Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/powerpc/platforms/powernv/pci-ioda.c | 37 ++++++++++++++++++++++++++++++ 1 file changed, 37 insertions(+)
--- a/arch/powerpc/platforms/powernv/pci-ioda.c +++ b/arch/powerpc/platforms/powernv/pci-ioda.c @@ -3368,12 +3368,49 @@ static void pnv_pci_ioda_create_dbgfs(vo #endif /* CONFIG_DEBUG_FS */ }
+static void pnv_pci_enable_bridge(struct pci_bus *bus) +{ + struct pci_dev *dev = bus->self; + struct pci_bus *child; + + /* Empty bus ? bail */ + if (list_empty(&bus->devices)) + return; + + /* + * If there's a bridge associated with that bus enable it. This works + * around races in the generic code if the enabling is done during + * parallel probing. This can be removed once those races have been + * fixed. + */ + if (dev) { + int rc = pci_enable_device(dev); + if (rc) + pci_err(dev, "Error enabling bridge (%d)\n", rc); + pci_set_master(dev); + } + + /* Perform the same to child busses */ + list_for_each_entry(child, &bus->children, node) + pnv_pci_enable_bridge(child); +} + +static void pnv_pci_enable_bridges(void) +{ + struct pci_controller *hose; + + list_for_each_entry(hose, &hose_list, list_node) + pnv_pci_enable_bridge(hose->bus); +} + static void pnv_pci_ioda_fixup(void) { pnv_pci_ioda_setup_PEs(); pnv_pci_ioda_setup_iommu_api(); pnv_pci_ioda_create_dbgfs();
+ pnv_pci_enable_bridges(); + #ifdef CONFIG_EEH pnv_eeh_post_init(); #endif