Re: [Xen-devel] [PATCH 2/5] xen/pciback: Support pci_reset_function, aka FLR or D3 support.

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

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@xxxxxxxxxx>
> ---
>  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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