Re: [RFC PATCH v2, part3 07/11] PCI, xen-pcifront: use new PCI interfaces to simplify implementation

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Thu, May 16, 2013 at 11:50:55PM +0800, Jiang Liu wrote:
> Use new PCI interfaces to simplify xen-pcifront implementation:
> 1) Use pci_create_root_bus() instead of pci_scan_bus_parented()
>    because pci_scan_bus_parented() is marked as __deprecated.This
>    also gets rid of a duplicated call of pci_bus_start_devices().
> 2) Use pci_stop_root_bus() and pci_remove_root_bus() instead of
>    open-coded private implementation.
> 3) Use pci_set_host_bridge_release() to release data structures
>    associated with PCI root buses.
> 4) Use pci_bus_get()/pci_bus_put() to manage PCI root bus reference
>    count.
> 
> This is also a preparation for coming PCI bus lock enhancement.
> 
> Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> Cc: Jeremy Fitzhardinge <jeremy@goop.org>
> Cc: xen-devel@lists.xensource.com
> Cc: virtualization@lists.linux-foundation.org
> Cc: linux-pci@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org
> ---
>  drivers/pci/xen-pcifront.c | 81 ++++++++++++++++++++++------------------------
>  1 file changed, 39 insertions(+), 42 deletions(-)
> 
> diff --git a/drivers/pci/xen-pcifront.c b/drivers/pci/xen-pcifront.c
> index 816cf94..6aa2c0f 100644
> --- a/drivers/pci/xen-pcifront.c
> +++ b/drivers/pci/xen-pcifront.c
> @@ -25,11 +25,6 @@
>  #define INVALID_GRANT_REF (0)
>  #define INVALID_EVTCHN    (-1)
>  
> -struct pci_bus_entry {
> -	struct list_head list;
> -	struct pci_bus *bus;
> -};
> -
>  #define _PDEVB_op_active		(0)
>  #define PDEVB_op_active			(1 << (_PDEVB_op_active))
>  
> @@ -47,12 +42,12 @@ struct pcifront_device {
>  	struct xen_pci_sharedinfo *sh_info;
>  	struct work_struct op_work;
>  	unsigned long flags;
> -
>  };
>  
>  struct pcifront_sd {
>  	int domain;
>  	struct pcifront_device *pdev;
> +	struct resource busn_res;
>  };
>  
>  static inline struct pcifront_device *
> @@ -67,6 +62,12 @@ static inline void pcifront_init_sd(struct pcifront_sd *sd,
>  {
>  	sd->domain = domain;
>  	sd->pdev = pdev;
> +
> +	/* Xen pci-backend doesn't export P2P bridges */
> +	sd->busn_res.start = bus;
> +	sd->busn_res.end = bus;
> +	sd->busn_res.flags = IORESOURCE_BUS;
> +	sd->busn_res.name = "PCI busn";
>  }
>  
>  static DEFINE_SPINLOCK(pcifront_dev_lock);
> @@ -441,12 +442,19 @@ static int pcifront_scan_bus(struct pcifront_device *pdev,
>  	return 0;
>  }
>  
> +static void pcifront_release_sd(struct pci_host_bridge *bridge)
> +{
> +	struct pcifront_sd *sd = bridge->release_data;
> +
> +	kfree(sd);
> +}
> +
>  static int pcifront_scan_root(struct pcifront_device *pdev,
>  				 unsigned int domain, unsigned int bus)
>  {
>  	struct pci_bus *b;
>  	struct pcifront_sd *sd = NULL;
> -	struct pci_bus_entry *bus_entry = NULL;
> +	LIST_HEAD(resources);
>  	int err = 0;
>  
>  #ifndef CONFIG_PCI_DOMAINS
> @@ -463,16 +471,18 @@ static int pcifront_scan_root(struct pcifront_device *pdev,
>  	dev_info(&pdev->xdev->dev, "Creating PCI Frontend Bus %04x:%02x\n",
>  		 domain, bus);
>  
> -	bus_entry = kmalloc(sizeof(*bus_entry), GFP_KERNEL);
> -	sd = kmalloc(sizeof(*sd), GFP_KERNEL);
> -	if (!bus_entry || !sd) {
> +	sd = kzalloc(sizeof(*sd), GFP_KERNEL);
> +	if (!sd) {
>  		err = -ENOMEM;
>  		goto err_out;
>  	}
>  	pcifront_init_sd(sd, domain, bus, pdev);
>  
> -	b = pci_scan_bus_parented(&pdev->xdev->dev, bus,
> -				  &pcifront_bus_ops, sd);
> +	pci_add_resource(&resources, &ioport_resource);
> +	pci_add_resource(&resources, &iomem_resource);
> +	pci_add_resource(&resources, &sd->busn_res);
> +	b = pci_create_root_bus(&pdev->xdev->dev, bus, &pcifront_bus_ops,
> +				sd, &resources);
>  	if (!b) {
>  		dev_err(&pdev->xdev->dev,
>  			"Error creating PCI Frontend Bus!\n");
> @@ -480,12 +490,14 @@ static int pcifront_scan_root(struct pcifront_device *pdev,
>  		goto err_out;
>  	}
>  
> -	bus_entry->bus = b;
> +	pci_set_host_bridge_release(to_pci_host_bridge(b->bridge),
> +				    pcifront_release_sd, sd);
>  
> -	list_add(&bus_entry->list, &pdev->root_buses);
> -
> -	/* pci_scan_bus_parented skips devices which do not have a have
> -	* devfn==0. The pcifront_scan_bus enumerates all devfn. */
> +	/*
> +	 * Every PCI physical device should have function 0, but that's not
> +	 * true for xen.

That is incorrect. There are two types of backends - one of them will
start at zero, but the other might not.

> +	 * So use pcifront_scan_bus() instead of pci_scan_child_bus().
> +	 */
>  	err = pcifront_scan_bus(pdev, domain, bus, b);
>  
>  	/* Claim resources before going "live" with our devices */
> @@ -497,7 +509,6 @@ static int pcifront_scan_root(struct pcifront_device *pdev,
>  	return err;
>  
>  err_out:
> -	kfree(bus_entry);
>  	kfree(sd);
>  
>  	return err;
> @@ -539,35 +550,19 @@ static int pcifront_rescan_root(struct pcifront_device *pdev,
>  	return err;
>  }
>  
> -static void free_root_bus_devs(struct pci_bus *bus)
> -{
> -	struct pci_dev *dev;
> -
> -	while (!list_empty(&bus->devices)) {
> -		dev = container_of(bus->devices.next, struct pci_dev,
> -				   bus_list);
> -		dev_dbg(&dev->dev, "removing device\n");
> -		pci_stop_and_remove_bus_device(dev);
> -	}
> -}
> -
>  static void pcifront_free_roots(struct pcifront_device *pdev)
>  {
> -	struct pci_bus_entry *bus_entry, *t;
> +	struct pcifront_sd *sd;
> +	struct pci_bus *bus;
>  
>  	dev_dbg(&pdev->xdev->dev, "cleaning up root buses\n");
>  
> -	list_for_each_entry_safe(bus_entry, t, &pdev->root_buses, list) {
> -		list_del(&bus_entry->list);
> -
> -		free_root_bus_devs(bus_entry->bus);
> -
> -		kfree(bus_entry->bus->sysdata);
> -
> -		device_unregister(bus_entry->bus->bridge);
> -		pci_remove_bus(bus_entry->bus);
> -
> -		kfree(bus_entry);
> +	for_each_pci_root_bus(bus) {
> +		sd = bus->sysdata;
> +		if (sd->pdev == pdev) {
> +			pci_stop_root_bus(bus);
> +			pci_remove_root_bus(bus);
> +		}
>  	}
>  }
>  
> @@ -670,6 +665,7 @@ static irqreturn_t pcifront_handler_aer(int irq, void *dev)
>  	schedule_pcifront_aer_op(pdev);
>  	return IRQ_HANDLED;
>  }
> +

Stray
>  static int pcifront_connect_and_init_dma(struct pcifront_device *pdev)
>  {
>  	int err = 0;
> @@ -705,6 +701,7 @@ static void pcifront_disconnect(struct pcifront_device *pdev)
>  
>  	spin_unlock(&pcifront_dev_lock);
>  }
> +

Stray
>  static struct pcifront_device *alloc_pdev(struct xenbus_device *xdev)
>  {
>  	struct pcifront_device *pdev;
> -- 
> 1.8.1.2
>