linux-kernel - Re: [RFC v5 2/7] PCI: Do not Use IORESOURCE_STARTALIGN to identify bridge resources

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Message-ID: <57047183.9000003@linux.vnet.ibm.com>
Date:	Wed, 6 Apr 2016 10:16:35 +0800
From:	Yongji Xie <xyjxie@...ux.vnet.ibm.com>
To:	Gavin Shan <gwshan@...ux.vnet.ibm.com>
Cc:	kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-pci@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
	linux-doc@...r.kernel.org, bhelgaas@...gle.com, corbet@....net,
	aik@...abs.ru, alex.williamson@...hat.com,
	benh@...nel.crashing.org, paulus@...ba.org, mpe@...erman.id.au,
	warrier@...ux.vnet.ibm.com, zhong@...ux.vnet.ibm.com,
	nikunj@...ux.vnet.ibm.com
Subject: Re: [RFC v5 2/7] PCI: Do not Use IORESOURCE_STARTALIGN to identify
 bridge resources

On 2016/4/6 8:55, Gavin Shan wrote:
> On Tue, Apr 05, 2016 at 09:43:30PM +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.
>>
>> In this patch, we try to use a more robust way
>> to identify bridge resources.
>>
>> Signed-off-by: Yongji Xie <xyjxie@...ux.vnet.ibm.com>
>> ---
>> drivers/pci/setup-bus.c |   10 +++++++---
>> 1 file changed, 7 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
>> index 7796d0a..bffcf1e 100644
>> --- a/drivers/pci/setup-bus.c
>> +++ b/drivers/pci/setup-bus.c
>> @@ -391,6 +391,7 @@ 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))
>> @@ -411,11 +412,14 @@ 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 (pci_is_bridge(dev_res->dev) &&
>> +			index >= PCI_BRIDGE_RESOURCES &&
>> +			index <= PCI_BRIDGE_RESOURCE_END)
>> 			continue;
> Yongji, the condition seems incorrect. According to the comments in
> the code, it's resizing bridge's windows. So I think the code would
> be something like below?
>
> 		if (!pci_is_bridge(dev_res->dev) ||
> 		    index < PCI_BRIDGE_RESOURCES ||
> 		    index > PCI_BRIDGE_RESOURCE_END)
> 			continue;

Yes. I made a mistake here. It should be something like
the above code.

Thanks,
Yongji

>> 		add_align = get_res_add_align(realloc_head, dev_res->res);
> Thanks,
> Gavin
>
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