Re: [PATCH] PCI/shpchp: fix a bus speed issue on hotplug

From: Michael S. Tsirkin
Date: Sat May 17 2014 - 14:48:37 EST


On Thu, May 15, 2014 at 12:41:46PM -0600, Bjorn Helgaas wrote:
> On Thu, May 01, 2014 at 05:35:48PM +0300, Marcel Apfelbaum wrote:
> > When a board is added, the shpchp driver checks if there
> > is a mismatch between the bridge's adapter and the bus speed.
> > If there is, it sets the subordinate speed (if there is no device on it).
> >
> > However, it takes the reference of the board speed from the primary bus
> > and not from the subordinate. If the primary bus is PCI and not PCIX/PCIe,
> > its speed is not updated and remains 0xff. As a result hotplug fails
> > with error: "Speed of bus ff and adapter 0 mismatch".
> >
> > Fixed that by checking the speed against the subordinate bus.
> >
> > Signed-off-by: Marcel Apfelbaum <marcel.a@xxxxxxxxxx>
> > Acked-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
>
> I think cpqphp has similar issues. But I can't test it and I don't know if
> anybody even uses it any more, so I'm just going to leave it alone.
>
> I reworked the changelog because I got confused about the bridge, adapter,
> board, and what was what. Let me know if the one below is inaccurate.

It's accurate I think. I only wish someone reworked the actual
shpchp code to avoid the confusing adapter/board terminology.

> I'll include this for v3.15 since it's a regression fix.
>
> Thanks,
> Bjorn
>
> commit be219b7f518a36f62d67f057e9d31ebe9674814f
> Author: Marcel Apfelbaum <marcel.a@xxxxxxxxxx>
> Date: Thu May 1 17:35:48 2014 +0300
>
> PCI: shpchp: Check bridge's secondary (not primary) bus speed
>
> When a new device is added below a hotplug bridge, the bridge's secondary
> bus speed and the device's bus speed must match. The shpchp driver
> previously checked the bridge's *primary* bus speed, not the secondary bus
> speed.
>
> This caused hot-add errors like:
>
> shpchp 0000:00:03.0: Speed of bus ff and adapter 0 mismatch
>
> Check the secondary bus speed instead.
>
> [bhelgaas: changelog]
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=75251
> Fixes: 3749c51ac6c1 ("PCI: Make current and maximum bus speeds part of the PCI core")
> Signed-off-by: Marcel Apfelbaum <marcel.a@xxxxxxxxxx>
> Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
> Acked-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
> CC: stable@xxxxxxxxxxxxxxx # v2.6.34+
>
> diff --git a/drivers/pci/hotplug/shpchp_ctrl.c b/drivers/pci/hotplug/shpchp_ctrl.c
> index 58499277903a..6efc2ec5e4db 100644
> --- a/drivers/pci/hotplug/shpchp_ctrl.c
> +++ b/drivers/pci/hotplug/shpchp_ctrl.c
> @@ -282,8 +282,8 @@ static int board_added(struct slot *p_slot)
> return WRONG_BUS_FREQUENCY;
> }
>
> - bsp = ctrl->pci_dev->bus->cur_bus_speed;
> - msp = ctrl->pci_dev->bus->max_bus_speed;
> + bsp = ctrl->pci_dev->subordinate->cur_bus_speed;
> + msp = ctrl->pci_dev->subordinate->max_bus_speed;
>
> /* Check if there are other slots or devices on the same bus */
> if (!list_empty(&ctrl->pci_dev->subordinate->devices))
--
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