1 files changed, 41 insertions, 0 deletions

diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index fdefa7dcd156..010e01c4bd43 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -131,6 +131,46 @@ is_enabled_store(struct device *dev, struct device_attribute *attr,
         return count;
 }
 
+static ssize_t
+msi_bus_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+        struct pci_dev *pdev = to_pci_dev(dev);
+
+        if (!pdev->subordinate)
+                return 0;
+
+        return sprintf (buf, "%u\n",
+                        !(pdev->subordinate->bus_flags & PCI_BUS_FLAGS_NO_MSI));
+}
+
+static ssize_t
+msi_bus_store(struct device *dev, struct device_attribute *attr,
+              const char *buf, size_t count)
+{
+        struct pci_dev *pdev = to_pci_dev(dev);
+
+        /* bad things may happen if the no_msi flag is changed
+         * while some drivers are loaded */
+        if (!capable(CAP_SYS_ADMIN))
+                return count;
+
+        if (!pdev->subordinate)
+                return count;
+
+        if (*buf == '0') {
+                pdev->subordinate->bus_flags |= PCI_BUS_FLAGS_NO_MSI;
+                dev_warn(&pdev->dev, "forced subordinate bus to not support MSI,"
+                         " bad things could happen.\n");
+        }
+
+        if (*buf == '1') {
+                pdev->subordinate->bus_flags &= ~PCI_BUS_FLAGS_NO_MSI;
+                dev_warn(&pdev->dev, "forced subordinate bus to support MSI,"
+                         " bad things could happen.\n");
+        }
+
+        return count;
+}
 
 struct device_attribute pci_dev_attrs[] = {
         __ATTR_RO(resource),
@@ -145,6 +185,7 @@ struct device_attribute pci_dev_attrs[] = {
         __ATTR(enable, 0600, is_enabled_show, is_enabled_store),
         __ATTR(broken_parity_status,(S_IRUGO|S_IWUSR),
                 broken_parity_status_show,broken_parity_status_store),
+        __ATTR(msi_bus, 0644, msi_bus_show, msi_bus_store),
         __ATTR_NULL,
 };