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

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Date:	Mon, 25 Jun 2007 22:49:37 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	"Keshavamurthy, Anil S" <anil.s.keshavamurthy@...el.com>
Cc:	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 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?

--- 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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