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

Yongji Xie
2016-06-21T03:00:55Z

On 2016/6/21 9:50, Bjorn Helgaas wrote:

> 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?

Now there are two kinds of additional resources in the list: bridge
resource and SR-IOV resource. Here we just want to fix the
additional alignment for bridge. But if SR-IOV resource get the
flag IORESOURCE_STARTALIGN which is not only for bridge, the
current check seems to be wrong. And kernel parameter
"resource_alignment" could set IORESOURCE_STARTALIGN for
SR-IOV resource with my next patch applied.

Thanks,
Yongji

>> 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
>>
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