linux-kernel - Re: [Xen-devel] [PATCH 2/5] xen/pciback: Support pci_reset

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Date:	Thu, 5 Jan 2012 10:24:11 +0000
From:	Ian Campbell <Ian.Campbell@...rix.com>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"jbarnes@...tuousgeek.org" <jbarnes@...tuousgeek.org>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>
Subject: Re: [Xen-devel] [PATCH 2/5] xen/pciback: Support
 pci_reset_function, aka FLR or D3 support.

On Thu, 2012-01-05 at 00:46 +0000, Konrad Rzeszutek Wilk wrote:
> We use the __pci_reset_function_locked to perform the action.
> Also on attaching ("bind") and detaching ("unbind") we save and
> restore the configuration states. When the device is disconnected
> from a guest we use the "pci_reset_function" to also reset the
> device before being passed to another guest.

Currently I thought the toolstack was supposed to do the reset (by
writing to the reset node in sysfs) as it was (de)assigning devices
to/from guests. That's not to say that there isn't an argument for
preferring to do it kernels side but it would be interesting to make
that argument explicitly.

I guess the toolstack doesn't currently save/restore the configuration
state, could it though? I guess the state is all available in sysfs. On
the other hand the kernel provides us with a very handy function which
Just Does It...

Ian.

> 
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
> ---
>  drivers/xen/xen-pciback/pci_stub.c |   41 +++++++++++++++++++++++++++++++++--
>  drivers/xen/xen-pciback/pciback.h  |    1 +
>  2 files changed, 39 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/xen/xen-pciback/pci_stub.c b/drivers/xen/xen-pciback/pci_stub.c
> index 8f06e1e..0ce0dc6 100644
> --- a/drivers/xen/xen-pciback/pci_stub.c
> +++ b/drivers/xen/xen-pciback/pci_stub.c
> @@ -85,19 +85,34 @@ static struct pcistub_device *pcistub_device_alloc(struct pci_dev *dev)
>  static void pcistub_device_release(struct kref *kref)
>  {
>  	struct pcistub_device *psdev;
> +	struct xen_pcibk_dev_data *dev_data;
>  
>  	psdev = container_of(kref, struct pcistub_device, kref);
> +	dev_data = pci_get_drvdata(psdev->dev);
>  
>  	dev_dbg(&psdev->dev->dev, "pcistub_device_release\n");
>  
>  	xen_unregister_device_domain_owner(psdev->dev);
>  
> -	/* Clean-up the device */
> +	/* Call the reset function which does not take lock as this
> +	 * is called from "unbind" which takes a device_lock mutex.
> +	 */
> +	__pci_reset_function_locked(psdev->dev);
> +	if (pci_load_and_free_saved_state(psdev->dev,
> +					  &dev_data->pci_saved_state)) {
> +		dev_dbg(&psdev->dev->dev, "Could not reload PCI state\n");
> +	} else
> +		pci_restore_state(psdev->dev);
> +
> +	/* Disable the device */
>  	xen_pcibk_reset_device(psdev->dev);
> +
> +	kfree(dev_data);
> +	pci_set_drvdata(psdev->dev, NULL);
> +
> +	/* Clean-up the device */
>  	xen_pcibk_config_free_dyn_fields(psdev->dev);
>  	xen_pcibk_config_free_dev(psdev->dev);
> -	kfree(pci_get_drvdata(psdev->dev));
> -	pci_set_drvdata(psdev->dev, NULL);
>  
>  	pci_dev_put(psdev->dev);
>  
> @@ -230,7 +245,17 @@ void pcistub_put_pci_dev(struct pci_dev *dev)
>  	/* Cleanup our device
>  	 * (so it's ready for the next domain)
>  	 */
> +
> +	/* This is OK - we are running from workqueue context
> +	 * and want to inhibit the user from fiddling with 'reset'
> +	 */
> +	pci_reset_function(dev);
> +	pci_restore_state(psdev->dev);
> +
> +	/* This disables the device. */
>  	xen_pcibk_reset_device(found_psdev->dev);
> +
> +	/* And cleanup up our emulated fields. */
>  	xen_pcibk_config_free_dyn_fields(found_psdev->dev);
>  	xen_pcibk_config_reset_dev(found_psdev->dev);
>  
> @@ -325,6 +350,16 @@ static int __devinit pcistub_init_device(struct pci_dev *dev)
>  	if (err)
>  		goto config_release;
>  
> +	dev_dbg(&dev->dev, "reseting (FLR, D3, etc) the device\n");
> +	__pci_reset_function_locked(dev);
> +
> +	/* We need the device active to save the state. */
> +	dev_dbg(&dev->dev, "save state of device\n");
> +	pci_save_state(dev);
> +	dev_data->pci_saved_state = pci_store_saved_state(dev);
> +	if (!dev_data->pci_saved_state)
> +		dev_err(&dev->dev, "Could not store PCI conf saved state!\n");
> +
>  	/* Now disable the device (this also ensures some private device
>  	 * data is setup before we export)
>  	 */
> diff --git a/drivers/xen/xen-pciback/pciback.h b/drivers/xen/xen-pciback/pciback.h
> index e9b4011..a7def01 100644
> --- a/drivers/xen/xen-pciback/pciback.h
> +++ b/drivers/xen/xen-pciback/pciback.h
> @@ -41,6 +41,7 @@ struct xen_pcibk_device {
>  
>  struct xen_pcibk_dev_data {
>  	struct list_head config_fields;
> +	struct pci_saved_state *pci_saved_state;
>  	unsigned int permissive:1;
>  	unsigned int warned_on_write:1;
>  	unsigned int enable_intx:1;


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