On Wed, Jan 04, 2012 at 01:43:08PM -0500, Konrad Rzeszutek Wilk wrote:
>
> I am looking at implementing the FLR functionality in the xen-pciback driver and
> found a mutex issue I am not entirely sure how to resolve.
>
> In essence I am trying to call pci_reset_function() when a PCI device is
> "attached" (using "bind") to the xen-pciback driver.
>
> This means that when a user does:
>
> echo "0000:01.07.0" > /sys/bus/pci/drivers/pciback/bind
>
> we end up calling:
> driver_bind:
> device_lock(dev);
> pcistub_probe:
> pcistub_seize:
> pcistub_init_device:
> .. pci_enable_device()
> --> want also to do pci_reset_function(), which calls
> pci_dev_reset(dev, 0):
> if (!0) {
> device_lock(dev) <==== DEADLOCK
>
> .. pci_disable_device()
>
> So looking at the code I saw __pci_reset_function which I thought
> would do the same as pci_reset_function but without locking.
> However, it is actually the opposite - it is with the locking.
>
> My thought is that one way to resolve this is by wrapping
> pci_probe_reset_function with a EXPORT_SYMBOL_GPL and use that
> instead. Or perhaps have a new function called
> "pci_reset_function_locked" ?
>
> Thoughts?
Here is what I am doing right now, which is hack-ish - I end up
unlocking the device_unlock(dev) to make it possible from user-space
to work:
So thinking of the 'psi_reset_function_locked" variant but not
sure if you are OK with it?
commit 591daec1a0b5f3528bd8480ea32c09551e7613ce
Author: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Date: Tue Jan 3 19:11:24 2012 -0500
xen/pciback: Support FLR/PM D3 reset of PCI devices.
Using the generic pci_reset_function call.
And also save the PM states of the PCI device and restore them.
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
diff --git a/drivers/xen/xen-pciback/pci_stub.c b/drivers/xen/xen-pciback/pci_stub.c
index 8f06e1e..e80eaec 100644
--- a/drivers/xen/xen-pciback/pci_stub.c
+++ b/drivers/xen/xen-pciback/pci_stub.c
@@ -85,19 +85,46 @@ 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 */
+ /* HACK: Check whether the release is driven from "unbind" which
+ * takes a mutex. */
+ if (device_trylock(&psdev->dev->dev)) {
+ /* nobody has the mutex, except us so unlock */
+ device_unlock(&psdev->dev->dev);
+ /* so that we can call reset. */
+ pci_reset_function(psdev->dev);
+ } else {
+ /* "unbind" called, so release the mutex. */
+ device_unlock(&psdev->dev->dev);
+ /* so that we can do the reset */
+ pci_reset_function(psdev->dev);
+ /* and then establish the mutex again. */
+ device_lock(&psdev->dev->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 +257,17 @@ 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);
@@ -325,12 +362,28 @@ 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");
+ /* HACK: Mutex is present if user did "bind" on the device. */
+ if (device_trylock(&dev->dev)) {
+ device_unlock(&dev->dev);
+ pci_reset_function(dev);
+ } else {
+ device_unlock(&dev->dev);
+ pci_reset_function(dev);
+ device_lock(&dev->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)
*/
- dev_dbg(&dev->dev, "reset device\n");
xen_pcibk_reset_device(dev);
-
return 0;
config_release:
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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