linux-kernel - Re: [Intel IOMMU 02/10] PCI generic helper function

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Message-ID: <20070626144453.GA31186@linux-os.sc.intel.com>
Date:	Tue, 26 Jun 2007 07:44:53 -0700
From:	"Keshavamurthy, Anil S" <anil.s.keshavamurthy@...el.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	"Keshavamurthy, Anil S" <anil.s.keshavamurthy@...el.com>,
	linux-kernel@...r.kernel.org, ak@...e.de, gregkh@...e.de,
	muli@...ibm.com, suresh.b.siddha@...el.com, arjan@...ux.intel.com,
	ashok.raj@...el.com, davem@...emloft.net, clameter@....com
Subject: Re: [Intel IOMMU 02/10] PCI generic helper function

On Mon, Jun 25, 2007 at 10:49:37PM -0700, Andrew Morton wrote:
> On Tue, 19 Jun 2007 14:37:03 -0700 "Keshavamurthy, Anil S" <anil.s.keshavamurthy@...el.com> wrote:
> 
> > +struct pci_dev *
> > +pci_find_upstream_pcie_bridge(struct pci_dev *pdev)
> 
> You didn't need a newline there, but that's what the rest of that file
> does.  Hu hum.
> 
> > +{
> > +	struct pci_dev *tmp = NULL;
> > +
> > +	if (pdev->is_pcie)
> > +		return NULL;
> > +	while (1) {
> > +		if (!pdev->bus->self)
> > +			break;
> > +		pdev = pdev->bus->self;
> > +		/* a p2p bridge */
> > +		if (!pdev->is_pcie) {
> > +			tmp = pdev;
> > +			continue;
> > +		}
> > +		/* PCI device should connect to a PCIE bridge */
> > +		BUG_ON(pdev->pcie_type != PCI_EXP_TYPE_PCI_BRIDGE);
> 
> I assume that if this bug triggers, we've found some broken hardware?
> 
> Going BUG seems like a pretty rude reaction to this, especially when it
> would be so easy to drop a warning and then recover.
> 
> 
> How's about this?
Looks good, thanks.

> 
> --- a/drivers/pci/search.c~intel-iommu-pci-generic-helper-function-fix
> +++ a/drivers/pci/search.c
> @@ -38,7 +38,11 @@ pci_find_upstream_pcie_bridge(struct pci
>  			continue;
>  		}
>  		/* PCI device should connect to a PCIE bridge */
> -		BUG_ON(pdev->pcie_type != PCI_EXP_TYPE_PCI_BRIDGE);
> +		if (pdev->pcie_type != PCI_EXP_TYPE_PCI_BRIDGE) {
> +			/* Busted hardware? */
> +			WARN_ON_ONCE(1);
> +			return NULL;
> +		}
>  		return pdev;
>  	}
>  
-
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