1 files changed, 14 insertions, 1 deletions

diff --git a/drivers/xen/xen-pciback/conf_space_header.c b/drivers/xen/xen-pciback/conf_space_header.c
index 2d7369391472..c2260a0456c9 100644
--- a/drivers/xen/xen-pciback/conf_space_header.c
+++ b/drivers/xen/xen-pciback/conf_space_header.c
@@ -88,9 +88,15 @@ static int command_write(struct pci_dev *dev, int offset, u16 value, void *data)
                         printk(KERN_DEBUG DRV_NAME ": %s: set bus master\n",
                                pci_name(dev));
                 pci_set_master(dev);
+        } else if (dev->is_busmaster && !is_master_cmd(value)) {
+                if (unlikely(verbose_request))
+                        printk(KERN_DEBUG DRV_NAME ": %s: clear bus master\n",
+                               pci_name(dev));
+                pci_clear_master(dev);
         }
 
-        if (value & PCI_COMMAND_INVALIDATE) {
+        if (!(cmd->val & PCI_COMMAND_INVALIDATE) &&
+            (value & PCI_COMMAND_INVALIDATE)) {
                 if (unlikely(verbose_request))
                         printk(KERN_DEBUG
                                DRV_NAME ": %s: enable memory-write-invalidate\n",
@@ -101,6 +107,13 @@ static int command_write(struct pci_dev *dev, int offset, u16 value, void *data)
                                 pci_name(dev), err);
                         value &= ~PCI_COMMAND_INVALIDATE;
                 }
+        } else if ((cmd->val & PCI_COMMAND_INVALIDATE) &&
+                   !(value & PCI_COMMAND_INVALIDATE)) {
+                if (unlikely(verbose_request))
+                        printk(KERN_DEBUG
+                               DRV_NAME ": %s: disable memory-write-invalidate\n",
+                               pci_name(dev));
+                pci_clear_mwi(dev);
         }
 
         cmd->val = value;