Re: [PATCH v5 1/5] PCI/AER: Fix pci_ops return NULL in pci_read/write_aer

[Huang Ying <ying.huang@intel.com>]

On Fri, 2012-09-21 at 16:43 +0800, Yijing Wang wrote:
> When we injected aer errors to the pcie device by aer_inject module, pci_ops of the pci
> bus the device on will be assigned to pci_ops_aer.So if the target pci device
> is a bridge, once we hot-remove and hot-add the bridge, the newly created child bus's pci_ops
> will be assigned to pci_ops_aer too.Now every access to the child bus's device will cause the
> system panic, because it will get a NULL pci_ops in pci_read_aer/pci_write_aer.
> 
> Signed-off-by: Yijing Wang <wangyijing@huawei.com>
> Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
> Reviewed-by: Sven Dietrich <Sven.Dietrich@huawei.com>

Reviewed-by: Huang Ying <ying.huang@intel.com>

> ---
>  drivers/pci/pcie/aer/aer_inject.c |   26 +++++++++++++++++++++++++-
>  1 files changed, 25 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/pci/pcie/aer/aer_inject.c b/drivers/pci/pcie/aer/aer_inject.c
> index 4e24cb8..fdab3bb 100644
> --- a/drivers/pci/pcie/aer/aer_inject.c
> +++ b/drivers/pci/pcie/aer/aer_inject.c
> @@ -109,6 +109,26 @@ static struct aer_error *__find_aer_error_by_dev(struct pci_dev *dev)
>  	return __find_aer_error((u16)domain, dev->bus->number, dev->devfn);
>  }
>  
> +/* find pci_ops of the nearest parent bus */
> +static struct pci_ops *__find_pci_bus_ops_parent(struct pci_bus *bus)
> +{
> +	struct pci_bus_ops *bus_ops;
> +	struct pci_bus *pbus = bus->parent;
> +
> +	if (!pbus)
> +		return NULL;
> +
> +	while (pbus) {
> +		list_for_each_entry(bus_ops, &pci_bus_ops_list, list)
> +			if (bus_ops->bus == pbus)
> +				return bus_ops->ops;
> +
> +		pbus = pbus->parent;
> +	}
> +
> +	return NULL;
> +}
> +
>  /* inject_lock must be held before calling */
>  static struct pci_ops *__find_pci_bus_ops(struct pci_bus *bus)
>  {
> @@ -118,7 +138,9 @@ static struct pci_ops *__find_pci_bus_ops(struct pci_bus *bus)
>  		if (bus_ops->bus == bus)
>  			return bus_ops->ops;
>  	}
> -	return NULL;
> +
> +	/* can't find bus_ops, fall back to get bus_ops of parent bus */
> +	return __find_pci_bus_ops_parent(bus);
>  }
>  
>  static struct pci_bus_ops *pci_bus_ops_pop(void)
> @@ -208,6 +230,7 @@ static int pci_read_aer(struct pci_bus *bus, unsigned int devfn, int where,
>  	}
>  out:
>  	ops = __find_pci_bus_ops(bus);
> +	BUG_ON(!ops);
>  	spin_unlock_irqrestore(&inject_lock, flags);
>  	return ops->read(bus, devfn, where, size, val);
>  }
> @@ -243,6 +266,7 @@ int pci_write_aer(struct pci_bus *bus, unsigned int devfn, int where, int size,
>  	}
>  out:
>  	ops = __find_pci_bus_ops(bus);
> +	BUG_ON(!ops);
>  	spin_unlock_irqrestore(&inject_lock, flags);
>  	return ops->write(bus, devfn, where, size, val);
>  }