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

[Yongji Xie]

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@xxxxxxxxxxxxxxxxxx>
> > ---
> >   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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