linux-kernel - Re: [RFC PATCH v2, part 2 16/18] PCI, iommu: use hotplug-safe iterators to walk PCI buses

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Date:	Tue, 14 May 2013 18:13:11 -0400
From:	Don Dutile <ddutile@...hat.com>
To:	Jiang Liu <liuj97@...il.com>
CC:	Bjorn Helgaas <bhelgaas@...gle.com>,
	Yinghai Lu <yinghai@...nel.org>,
	Jiang Liu <jiang.liu@...wei.com>,
	"Rafael J . Wysocki" <rjw@...k.pl>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Gu Zheng <guz.fnst@...fujitsu.com>,
	Toshi Kani <toshi.kani@...com>,
	Myron Stowe <myron.stowe@...hat.com>,
	Yijing Wang <wangyijing@...wei.com>, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org, Joerg Roedel <joro@...tes.org>,
	Ingo Molnar <mingo@...nel.org>, Hannes Reinecke <hare@...e.de>,
	"Li, Zhen-Hua" <zhen-hual@...com>, iommu@...ts.linux-foundation.org
Subject: Re: [RFC PATCH v2, part 2 16/18] PCI, iommu: use hotplug-safe iterators
 to walk PCI buses

On 05/14/2013 12:52 PM, Jiang Liu wrote:
> Enhance iommu drviers to use hotplug-safe iterators to walk
> PCI buses.
>
> Signed-off-by: Jiang Liu<jiang.liu@...wei.com>
> Cc: Joerg Roedel<joro@...tes.org>
> Cc: Ingo Molnar<mingo@...nel.org>
> Cc: Donald Dutile<ddutile@...hat.com>
> Cc: Hannes Reinecke<hare@...e.de>
> Cc: "Li, Zhen-Hua"<zhen-hual@...com>
> Cc: iommu@...ts.linux-foundation.org
> Cc: linux-kernel@...r.kernel.org
> ---
>   drivers/iommu/amd_iommu.c | 4 +++-
>   drivers/iommu/dmar.c      | 6 ++++--
>   2 files changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
> index e046d7a..d6fdf94 100644
> --- a/drivers/iommu/amd_iommu.c
> +++ b/drivers/iommu/amd_iommu.c
> @@ -357,6 +357,7 @@ static int init_iommu_group(struct device *dev)
>   	struct iommu_dev_data *dev_data;
>   	struct iommu_group *group;
>   	struct pci_dev *dma_pdev;
> +	struct pci_bus *b = NULL;
>   	int ret;
>
>   	group = iommu_group_get(dev);
> @@ -393,7 +394,7 @@ static int init_iommu_group(struct device *dev)
>   		 * the alias.  Be careful to also test the parent device if
>   		 * we think the alias is the root of the group.
>   		 */
> -		bus = pci_find_bus(0, alias>>  8);
> +		b = bus = pci_find_bus(0, alias>>  8);
>   		if (!bus)
>   			goto use_group;
>
> @@ -413,6 +414,7 @@ static int init_iommu_group(struct device *dev)
>   	dma_pdev = get_isolation_root(pci_dev_get(to_pci_dev(dev)));
>   use_pdev:
>   	ret = use_pdev_iommu_group(dma_pdev, dev);
> +	pci_bus_put(b);
pci_find_bus() does a pci_bus_put() after the pci_get_bus();
is this needed, or did you mean to make the above patch pci_get_bus() ?

>   	pci_dev_put(dma_pdev);
>   	return ret;
>   use_group:
> diff --git a/drivers/iommu/dmar.c b/drivers/iommu/dmar.c
> index e5cdaf8..5bb3cdc 100644
> --- a/drivers/iommu/dmar.c
> +++ b/drivers/iommu/dmar.c
> @@ -67,12 +67,12 @@ static void __init dmar_register_drhd_unit(struct dmar_drhd_unit *drhd)
>   static int __init dmar_parse_one_dev_scope(struct acpi_dmar_device_scope *scope,
>   					   struct pci_dev **dev, u16 segment)
>   {
> -	struct pci_bus *bus;
> +	struct pci_bus *b, *bus;
>   	struct pci_dev *pdev = NULL;
>   	struct acpi_dmar_pci_path *path;
>   	int count;
>
> -	bus = pci_find_bus(segment, scope->bus);
> +	b = bus = pci_find_bus(segment, scope->bus);
>   	path = (struct acpi_dmar_pci_path *)(scope + 1);
>   	count = (scope->length - sizeof(struct acpi_dmar_device_scope))
>   		/ sizeof(struct acpi_dmar_pci_path);
> @@ -97,6 +97,8 @@ static int __init dmar_parse_one_dev_scope(struct acpi_dmar_device_scope *scope,
>   		count --;
>   		bus = pdev->subordinate;
>   	}
> +	pci_bus_put(b);
ditto.

> +
>   	if (!pdev) {
>   		pr_warn("Device scope device [%04x:%02x:%02x.%02x] not found\n",
>   			segment, scope->bus, path->dev, path->fn);

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