linux-kernel - Re: [PATCH v3 3/3] xen/pciback: support driver

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Date:   Thu, 22 Sep 2016 17:10:55 -0400
From:   Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:     Juergen Gross <jgross@...e.com>, linux-kernel@...r.kernel.org,
        xen-devel@...ts.xenproject.org
Cc:     david.vrabel@...rix.com
Subject: Re: [PATCH v3 3/3] xen/pciback: support driver_override

On 09/22/2016 04:45 AM, Juergen Gross wrote:
> Support the driver_override scheme introduced with commit 782a985d7af2
> ("PCI: Introduce new device binding path using pci_dev.driver_override")
>
> As pcistub_probe() is called for all devices (it has to check for a
> match based on the slot address rather than device type) it has to
> check for driver_override set to "pciback" itself.
>
> Up to now for assigning a pci device to pciback you need something like:
>
> echo 0000:07:10.0 > /sys/bus/pci/devices/0000\:07\:10.0/driver/unbind
> echo 0000:07:10.0 > /sys/bus/pci/drivers/pciback/new_slot
> echo 0000:07:10.0 > /sys/bus/pci/drivers_probe
>
> while with the patch you can use the same mechanism as for similar
> drivers like pci-stub and vfio-pci:
>
> echo pciback > /sys/bus/pci/devices/0000\:07\:10.0/driver_override
> echo 0000:07:10.0 > /sys/bus/pci/devices/0000\:07\:10.0/driver/unbind
> echo 0000:07:10.0 > /sys/bus/pci/drivers_probe
>
> So e.g. libvirt doesn't need special handling for pciback.
>
> Signed-off-by: Juergen Gross <jgross@...e.com>
> ---
> V3: Move override check up in order not to miss the PCI_HEADER_TYPE
>     check.
>     Add an assigned device to the slot list.
>
> V2: Removed now unused label
> ---
>  drivers/xen/xen-pciback/pci_stub.c | 36 +++++++++++++++++++++++++++++-------
>  1 file changed, 29 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/xen/xen-pciback/pci_stub.c b/drivers/xen/xen-pciback/pci_stub.c
> index 0179333..6331a95 100644
> --- a/drivers/xen/xen-pciback/pci_stub.c
> +++ b/drivers/xen/xen-pciback/pci_stub.c
> @@ -25,6 +25,8 @@
>  #include "conf_space.h"
>  #include "conf_space_quirks.h"
>  
> +#define PCISTUB_DRIVER_NAME "pciback"
> +
>  static char *pci_devs_to_hide;
>  wait_queue_head_t xen_pcibk_aer_wait_queue;
>  /*Add sem for sync AER handling and xen_pcibk remove/reconfigue ops,
> @@ -508,15 +510,18 @@ static void pcistub_device_id_add_list(struct pcistub_device_id *new,
>  		kfree(new);
>  }
>  
> -static int pcistub_seize(struct pci_dev *dev)
> +static int pcistub_seize(struct pci_dev *dev,
> +			 struct pcistub_device_id *pci_dev_id)
>  {
>  	struct pcistub_device *psdev;
>  	unsigned long flags;
>  	int err = 0;
>  
>  	psdev = pcistub_device_alloc(dev);
> -	if (!psdev)
> +	if (!psdev) {
> +		kfree(pci_dev_id);

Here too --- I'd rather have it freed by whoever allocated it (i.e. the
caller). In fact I think you can allocate this here and instead of
passing pci_dev_id pointer pass a flag of some sort.


-boris

>  		return -ENOMEM;
> +	}
>  
>  	spin_lock_irqsave(&pcistub_devices_lock, flags);
>  
> @@ -537,8 +542,12 @@ static int pcistub_seize(struct pci_dev *dev)
>  
>  	spin_unlock_irqrestore(&pcistub_devices_lock, flags);
>  
> -	if (err)
> +	if (err) {
> +		kfree(pci_dev_id);
>  		pcistub_device_put(psdev);
> +	} else if (pci_dev_id)
> +		pcistub_device_id_add_list(pci_dev_id, pci_domain_nr(dev->bus),
> +					   dev->bus->number, dev->devfn);
>  
>  	return err;
>  }
> @@ -547,11 +556,16 @@ static int pcistub_seize(struct pci_dev *dev)
>   * other functions that take the sysfs lock. */
>  static int pcistub_probe(struct pci_dev *dev, const struct pci_device_id *id)
>  {
> -	int err = 0;
> +	int err = 0, match;
> +	struct pcistub_device_id *pci_dev_id = NULL;
>  
>  	dev_dbg(&dev->dev, "probing...\n");
>  
> -	if (pcistub_match(dev)) {
> +	match = pcistub_match(dev);
> +
> +	if ((dev->driver_override &&
> +	     !strcmp(dev->driver_override, PCISTUB_DRIVER_NAME)) ||
> +	    match) {
>  
>  		if (dev->hdr_type != PCI_HEADER_TYPE_NORMAL
>  		    && dev->hdr_type != PCI_HEADER_TYPE_BRIDGE) {
> @@ -562,8 +576,16 @@ static int pcistub_probe(struct pci_dev *dev, const struct pci_device_id *id)
>  			goto out;
>  		}
>  
> +		if (!match) {
> +			pci_dev_id = kmalloc(sizeof(*pci_dev_id), GFP_ATOMIC);
> +			if (!pci_dev_id) {
> +				err = -ENOMEM;
> +				goto out;
> +			}
> +		}
> +
>  		dev_info(&dev->dev, "seizing device\n");
> -		err = pcistub_seize(dev);
> +		err = pcistub_seize(dev, pci_dev_id);
>  	} else
>  		/* Didn't find the device */
>  		err = -ENODEV;
> @@ -975,7 +997,7 @@ static const struct pci_error_handlers xen_pcibk_error_handler = {
>  static struct pci_driver xen_pcibk_pci_driver = {
>  	/* The name should be xen_pciback, but until the tools are updated
>  	 * we will keep it as pciback. */
> -	.name = "pciback",
> +	.name = PCISTUB_DRIVER_NAME,
>  	.id_table = pcistub_ids,
>  	.probe = pcistub_probe,
>  	.remove = pcistub_remove,