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

From: Ian Campbell
Date: Thu Jan 05 2012 - 05:24:20 EST


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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