Subject: Re: [1/3] powerpc/vfio: Enable on POWERNV platform

From: Scott Wood <[email-masked]>
Date: Thu, 12 Dec 2013 17:35:27 -0600

On Tue, May 21, 2013 at 01:33:09PM +1000, Alexey Kardashevskiy wrote:
> +static int iommu_add_device(struct device *dev)
> +{
> +	struct iommu_table *tbl;
> +	int ret = 0;
> +
> +	if (WARN_ON(dev->iommu_group)) {
> +		pr_warn("iommu_tce: device %s is already in iommu group %d, skipping\n",
> +				dev_name(dev),
> +				iommu_group_id(dev->iommu_group));
> +		return -EBUSY;
> +	}
[snip]
> +static int __init tce_iommu_init(void)
> +{
> +	struct pci_dev *pdev = NULL;
> +
> +	BUILD_BUG_ON(PAGE_SIZE < IOMMU_PAGE_SIZE);
> +
> +	for_each_pci_dev(pdev)
> +		iommu_add_device(&pdev->dev);
> +
> +	bus_register_notifier(&pci_bus_type, &tce_iommu_bus_nb);
> +	return 0;
> +}
> +
> +subsys_initcall_sync(tce_iommu_init);

This is missing a check to see whether the appropriate hardware is
present.  This file should also be renamed to something less generic, and
depend on a kconfig symbol more specific than CONFIG_PPC64.

When this is combined with CONFIG_FSL_PAMU on hardware with a PAMU, I get
a bunch of those "WARN_ON(dev->iommu_group)" dumps because PAMU already
got to them.  Presumably without PAMU it silently (or with just pr_debug)
bails out at some other point.

-Scott