Re: [PATCH v2 1/2] iommu: Quirked PCIe bridge test and search function

[Joerg Roedel <joro-zLv9SwRftAIdnm+yROfE0A@public.gmane.org>]

On Tue, May 28, 2013 at 12:40:20PM -0600, Alex Williamson wrote:
> +bool iommu_pci_is_pcie_bridge(struct pci_dev *pdev)
> +{
> +	if (!pdev->subordinate)
> +		return false;
> +
> +	if (pci_is_pcie(pdev))
> +		return true;
> +
> +#ifdef CONFIG_PCI_QUIRKS
> +	/*
> +	 * If we're not on the root bus, look one device upstream of the
> +	 * current device.  If that device is PCIe and is not a PCIe-to-PCI
> +	 * bridge, then the current device is effectively PCIe as it must
> +	 * be the PCIe-to-PCI bridge.  This handles several bridges that
> +	 * violate the PCIe spec by not exposing a PCIe capability:
> +	 * https://bugzilla.kernel.org/show_bug.cgi?id=44881
> +	 */
> +	if (!pci_is_root_bus(pdev->bus)) {
> +		struct pci_dev *parent = pdev->bus->self;
> +
> +		if (pci_is_pcie(parent) &&
> +		    pci_pcie_type(parent) != PCI_EXP_TYPE_PCI_BRIDGE)
> +			return true;
> +	}

Hmm, that looks a bit dangerous. Do we have a list of PCI
vendor/device-ids of these broken bridges to match against instead of
some open-coded heuristics?

That would probably also help to bring this into the PCI code.


	Joerg