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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH 2/2] xen-pciback: provide a "reset" sysfs file to try harder at an SBR
The standard implementation of pci_reset_function() does not try an
SBR if there are other sibling devices. This is a common
configuration for multi-function devices (e.g., GPUs with a HDMI audio
device function).
If all the functions are co-assigned to the same domain at the same
time, then it is safe to perform an SBR to reset all functions at the
same time.
Add a "reset" sysfs file with the same interface as the standard one
(i.e., write 1 to reset) that will try an SBR if all sibling devices
are unbound or bound to pciback.
Note that this is weaker than the requirement for functions to be
simultaneously co-assigned, but the toolstack is expected to ensure
this.
Signed-off-by: David Vrabel <david.vrabel@xxxxxxxxxx>
---
Changes in v3:
- probe for function reset
- use pci_reset_bus().
Changes in v2:
- defer creating sysfs node to late init.
---
drivers/xen/xen-pciback/pci_stub.c | 107 +++++++++++++++++++++++++++++++++++-
drivers/xen/xen-pciback/pciback.h | 1 +
2 files changed, 105 insertions(+), 3 deletions(-)
diff --git a/drivers/xen/xen-pciback/pci_stub.c
b/drivers/xen/xen-pciback/pci_stub.c
index d57a173..c7deceb 100644
--- a/drivers/xen/xen-pciback/pci_stub.c
+++ b/drivers/xen/xen-pciback/pci_stub.c
@@ -63,6 +63,100 @@ static LIST_HEAD(pcistub_devices);
static int initialize_devices;
static LIST_HEAD(seized_devices);
+/*
+ * pci_reset_function() will only work if there is a mechanism to
+ * reset that single function (e.g., FLR or a D-state transition).
+ * For PCI hardware that has two or more functions but no per-function
+ * reset, we can do a bus reset iff all the functions are co-assigned
+ * to the same domain.
+ *
+ * If a function has no per-function reset mechanism the 'reset' sysfs
+ * file that the toolstack uses to reset a function prior to assigning
+ * the device will be missing. In this case, pciback adds its own
+ * which will try a bus reset.
+ *
+ * Note: pciback does not check for co-assigment before doing a bus
+ * reset, only that the devices are bound to pciback. The toolstack
+ * is assumed to have done the right thing.
+ */
+static int __pcistub_reset_function(struct pci_dev *dev)
+{
+ struct pci_dev *pdev;
+ int ret;
+
+ ret = __pci_reset_function_locked(dev);
+ if (ret == 0)
+ return 0;
+
+ if (pci_is_root_bus(dev->bus) || dev->subordinate || !dev->bus->self)
+ return -ENOTTY;
+
+ list_for_each_entry(pdev, &dev->bus->devices, bus_list) {
+ if (pdev != dev && (!pdev->driver
+ || strcmp(pdev->driver->name, "pciback")))
+ return -ENOTTY;
+ }
+
+ return pci_reset_bus(dev->bus);
+}
+
+static int pcistub_reset_function(struct pci_dev *dev)
+{
+ int ret;
+
+ device_lock(&dev->dev);
+ ret = __pcistub_reset_function(dev);
+ device_unlock(&dev->dev);
+
+ return ret;
+}
+
+static ssize_t pcistub_reset_store(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ struct pci_dev *pdev = to_pci_dev(dev);
+ unsigned long val;
+ ssize_t result = strict_strtoul(buf, 0, &val);
+
+ if (result < 0)
+ return result;
+
+ if (val != 1)
+ return -EINVAL;
+
+ result = pcistub_reset_function(pdev);
+ if (result < 0)
+ return result;
+ return count;
+}
+static DEVICE_ATTR(reset, 0200, NULL, pcistub_reset_store);
+
+static int pcistub_try_create_reset_file(struct pci_dev *pci)
+{
+ struct xen_pcibk_dev_data *dev_data = pci_get_drvdata(pci);
+ struct device *dev = &pci->dev;
+ int ret;
+
+ /* Already have a per-function reset? */
+ if (pci_probe_reset_function(pci) == 0)
+ return 0;
+
+ ret = device_create_file(dev, &dev_attr_reset);
+ if (ret < 0)
+ return ret;
+ dev_data->created_reset_file = true;
+ return 0;
+}
+
+static void pcistub_remove_reset_file(struct pci_dev *pci)
+{
+ struct xen_pcibk_dev_data *dev_data = pci_get_drvdata(pci);
+
+ if (dev_data && dev_data->created_reset_file)
+ device_remove_file(&pci->dev, &dev_attr_reset);
+}
+
static struct pcistub_device *pcistub_device_alloc(struct pci_dev *dev)
{
struct pcistub_device *psdev;
@@ -103,7 +197,8 @@ static void pcistub_device_release(struct kref *kref)
/* 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(dev);
+ __pcistub_reset_function(psdev->dev);
+
if (pci_load_and_free_saved_state(dev, &dev_data->pci_saved_state))
dev_dbg(&dev->dev, "Could not reload PCI state\n");
else
@@ -280,7 +375,7 @@ void pcistub_put_pci_dev(struct pci_dev *dev)
/* This is OK - we are running from workqueue context
* and want to inhibit the user from fiddling with 'reset'
*/
- pci_reset_function(dev);
+ pcistub_reset_function(dev);
pci_restore_state(dev);
/* This disables the device. */
@@ -404,7 +499,7 @@ static int pcistub_init_device(struct pci_dev *dev)
dev_err(&dev->dev, "Could not store PCI conf saved state!\n");
else {
dev_dbg(&dev->dev, "resetting (FLR, D3, etc) the device\n");
- __pci_reset_function_locked(dev);
+ __pcistub_reset_function(dev);
pci_restore_state(dev);
}
/* Now disable the device (this also ensures some private device
@@ -413,6 +508,10 @@ static int pcistub_init_device(struct pci_dev *dev)
dev_dbg(&dev->dev, "reset device\n");
xen_pcibk_reset_device(dev);
+ err = pcistub_try_create_reset_file(dev);
+ if (err < 0)
+ goto config_release;
+
dev->dev_flags |= PCI_DEV_FLAGS_ASSIGNED;
return 0;
@@ -540,6 +639,8 @@ static void pcistub_remove(struct pci_dev *dev)
dev_dbg(&dev->dev, "removing\n");
+ pcistub_remove_reset_file(dev);
+
spin_lock_irqsave(&pcistub_devices_lock, flags);
xen_pcibk_config_quirk_release(dev);
diff --git a/drivers/xen/xen-pciback/pciback.h
b/drivers/xen/xen-pciback/pciback.h
index f72af87..708ade9 100644
--- a/drivers/xen/xen-pciback/pciback.h
+++ b/drivers/xen/xen-pciback/pciback.h
@@ -42,6 +42,7 @@ struct xen_pcibk_device {
struct xen_pcibk_dev_data {
struct list_head config_fields;
struct pci_saved_state *pci_saved_state;
+ bool created_reset_file;
unsigned int permissive:1;
unsigned int warned_on_write:1;
unsigned int enable_intx:1;
--
1.7.10.4
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