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

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On 01/05/2012 05:24 AM, Ian Campbell wrote:
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
pci_reset_function() saves the config state before doing a fcn-level reset.

the libvirt toolstack handles the unbind/reset/bind functionality
and is used by kvm for it's device assignment.

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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