Re: [PATCHv6 2/7] pci: child bus alloc fix on constrained resource

[Keith Busch]

On Thu, Dec 17, 2015 at 11:27:18AM -0600, Bjorn Helgaas wrote:
> On Mon, Dec 07, 2015 at 02:32:24PM -0700, Keith Busch wrote:
> > +	if (busnr > parent->busn_res.end) {
> > +		dev_printk(KERN_DEBUG, &parent->dev,
> > +			  "can not alloc bus:%d under %pR\n", busnr,
> > +			  &parent->busn_res);
> > +		return NULL;
> 
> Can you take a look at 1820ffdccb9b ("PCI: Make sure bus number resources
> stay within their parents bounds") and 12d8706963f0 ("Revert "PCI: Make
> sure bus number resources stay within their parents bounds"")?
> 
> This is implemented differently, but it seems like it might expose the same
> problem we found with 1820ffdccb9b.
> 
> If you could take a look and confirm that "no, this does something
> differently than 1820ffdccb9b did" or "yes, this might expose that problem
> again," that would help.

Thank you for the references. I think 1820ffdccb9b had the check too
late, creating the child bus with resource conflicts. That'd probably
make it appear unavailable. But I believe this new proposal will still
break the same setup for a different reason.

We can live with this issue for now if we want to drop this patch from
the series. The only way we encounter a problem is when the config space
aperture is artificially constrained, so I can request the feature be
put on hold while a better fix is developed.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/