Re: [RESEND PATCH v2 2/4] PCI: Do not Use IORESOURCE_STARTALIGN to identify bridge resources

Bjorn Helgaas
2016-06-21T02:00:15Z

On Thu, Jun 02, 2016 at 01:46:49PM +0800, Yongji Xie wrote:
> Now we use the IORESOURCE_STARTALIGN to identify bridge resources
> in __assign_resources_sorted(). That's quite fragile. We can't
> make sure that the PCI devices' resources will not use
> IORESOURCE_STARTALIGN any more.

Can you explain this a little more? I don't quite understand the
problem. Maybe you can give an example of the problem?

> In this patch, we try to use a more robust way to identify
> bridge resources.
>
> Signed-off-by: Yongji Xie <xyjxie@linux.vnet.ibm.com>
> ---
> drivers/pci/setup-bus.c | 9 ++++++---
> 1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
> index 55641a3..216ddbc 100644
> --- a/drivers/pci/setup-bus.c
> +++ b/drivers/pci/setup-bus.c
> @@ -390,6 +390,7 @@ static void __assign_resources_sorted(struct list_head *head,
> struct pci_dev_resource *dev_res, *tmp_res, *dev_res2;
> unsigned long fail_type;
> resource_size_t add_align, align;
> + int index;
>
> /* Check if optional add_size is there */
> if (!realloc_head || list_empty(realloc_head))
> @@ -410,11 +411,13 @@ static void __assign_resources_sorted(struct list_head *head,
>
> /*
> * There are two kinds of additional resources in the list:
> - * 1. bridge resource -- IORESOURCE_STARTALIGN
> - * 2. SR-IOV resource -- IORESOURCE_SIZEALIGN
> + * 1. bridge resource
> + * 2. SR-IOV resource
> * Here just fix the additional alignment for bridge
> */
> - if (!(dev_res->res->flags & IORESOURCE_STARTALIGN))
> + index = dev_res->res - dev_res->dev->resource;
> + if (index < PCI_BRIDGE_RESOURCES ||
> + index > PCI_BRIDGE_RESOURCE_END)

I think the code looks OK; at least, it seems to match the comment.
I'd just like to understand the problem a little better.

> continue;
>
> add_align = get_res_add_align(realloc_head, dev_res->res);
> --
> 1.7.9.5
>