On Thu, Feb 15, 2018 at 3:39 PM, Mika Westerberg
<mika.westerberg@xxxxxxxxxxxxxxx> wrote:
> When distributing extra buses between hotplug bridges we need to make
> sure each bridge reserve at least one bus number, even if there is
> currently nothing connected to it. For instance ACPI hotplug may bring
> in additional devices to non-hotplug bridges later on. To make sure we
> don't run out of bus numbers for non-hotplug bridges reserve one bus
> number for them upfront before distributing buses for hotplug bridges.
>
> Fixes: 1c02ea810065 ("PCI: Distribute available buses to hotplug-capable bridges")
> Reported-by: Mario Limonciello <mario.limonciello@xxxxxxxx>
> Signed-off-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> ---
> drivers/pci/probe.c | 11 ++++++++---
> 1 file changed, 8 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index ef5377438a1e..6cefd47556e3 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -2561,7 +2561,10 @@ static unsigned int pci_scan_child_bus_extend(struct pci_bus *bus,
> for_each_pci_bridge(dev, bus) {
> cmax = max;
> max = pci_scan_bridge_extend(bus, dev, max, 0, 0);
> - used_buses += cmax - max;
> + /* Reserve one bus for each bridge */
> + used_buses++;
> + if (cmax - max > 1)
> + used_buses += cmax - max - 1;
> }
>
> /* Scan bridges that need to be reconfigured */
> @@ -2584,12 +2587,14 @@ static unsigned int pci_scan_child_bus_extend(struct pci_bus *bus,
> * bridges if any.
> */
> buses = available_buses / hotplug_bridges;
> - buses = min(buses, available_buses - used_buses);
> + buses = min(buses, available_buses - used_buses + 1);
> }
>
> cmax = max;
> max = pci_scan_bridge_extend(bus, dev, cmax, buses, 1);
> - used_buses += max - cmax;
> + /* One bus is already accounted so don't add it again */
> + if (max - cmax > 1)
> + used_buses += max - cmax - 1;
> }
>
> /*
> --
> 2.15.1
>
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