PCI: expose function reset capability in sysfs

Some devices allow an individual function to be reset without affecting
other functions in the same device: that's what pci_reset_function does.
For devices that have this support, expose reset attribite in sysfs.

This is useful e.g. for virtualization, where a qemu userspace
process wants to reset the device when the guest is reset,
to emulate machine reboot as closely as possible.

Acked-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>

3 files changed, 54 insertions, 0 deletions

diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index 85ebd02a64a7..0f6382f090ee 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -916,6 +916,24 @@ int __attribute__ ((weak)) pcibios_add_platform_entries(struct pci_dev *dev)
         return 0;
 }
 
+static ssize_t 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;
+        return pci_reset_function(pdev);
+}
+
+static struct device_attribute reset_attr = __ATTR(reset, 0200, NULL, reset_store);
+
 static int pci_create_capabilities_sysfs(struct pci_dev *dev)
 {
         int retval;
@@ -943,7 +961,22 @@ static int pci_create_capabilities_sysfs(struct pci_dev *dev)
         /* Active State Power Management */
         pcie_aspm_create_sysfs_dev_files(dev);
 
+        if (!pci_probe_reset_function(dev)) {
+                retval = device_create_file(&dev->dev, &reset_attr);
+                if (retval)
+                        goto error;
+                dev->reset_fn = 1;
+        }
         return 0;
+
+error:
+        pcie_aspm_remove_sysfs_dev_files(dev);
+        if (dev->vpd && dev->vpd->attr) {
+                sysfs_remove_bin_file(&dev->dev.kobj, dev->vpd->attr);
+                kfree(dev->vpd->attr);
+        }
+
+        return retval;
 }
 
 int __must_check pci_create_sysfs_dev_files (struct pci_dev *pdev)
@@ -1037,6 +1070,10 @@ static void pci_remove_capabilities_sysfs(struct pci_dev *dev)
         }
 
         pcie_aspm_remove_sysfs_dev_files(dev);
+        if (dev->reset_fn) {
+                device_remove_file(&dev->dev, &reset_attr);
+                dev->reset_fn = 0;
+        }
 }
 
 /**
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 7b70312181d7..7d55039ffa05 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -2262,6 +2262,22 @@ int __pci_reset_function(struct pci_dev *dev)
 EXPORT_SYMBOL_GPL(__pci_reset_function);
 
 /**
+ * pci_probe_reset_function - check whether the device can be safely reset
+ * @dev: PCI device to reset
+ *
+ * Some devices allow an individual function to be reset without affecting
+ * other functions in the same device.  The PCI device must be responsive
+ * to PCI config space in order to use this function.
+ *
+ * Returns 0 if the device function can be reset or negative if the
+ * device doesn't support resetting a single function.
+ */
+int pci_probe_reset_function(struct pci_dev *dev)
+{
+        return pci_dev_reset(dev, 1);
+}
+
+/**
  * pci_reset_function - quiesce and reset a PCI device function
  * @dev: PCI device to reset
  *
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index 5ff4d25bf0e9..73d9d92715a0 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -16,6 +16,7 @@ extern void pci_cleanup_rom(struct pci_dev *dev);
 extern int pci_mmap_fits(struct pci_dev *pdev, int resno,
                          struct vm_area_struct *vma);
 #endif
+int pci_probe_reset_function(struct pci_dev *dev);
 
 /**
  * struct pci_platform_pm_ops - Firmware PM callbacks