3 files changed, 51 insertions, 14 deletions

diff --git a/drivers/xen/xen-pciback/conf_space.c b/drivers/xen/xen-pciback/conf_space.c
index 46ae0f9f02ad..75fe3d466515 100644
--- a/drivers/xen/xen-pciback/conf_space.c
+++ b/drivers/xen/xen-pciback/conf_space.c
@@ -16,7 +16,7 @@
 #include "conf_space.h"
 #include "conf_space_quirks.h"
 
-static bool permissive;
+bool permissive;
 module_param(permissive, bool, 0644);
 
 /* This is where xen_pcibk_read_config_byte, xen_pcibk_read_config_word,
diff --git a/drivers/xen/xen-pciback/conf_space.h b/drivers/xen/xen-pciback/conf_space.h
index e56c934ad137..2e1d73d1d5d0 100644
--- a/drivers/xen/xen-pciback/conf_space.h
+++ b/drivers/xen/xen-pciback/conf_space.h
@@ -64,6 +64,8 @@ struct config_field_entry {
         void *data;
 };
 
+extern bool permissive;
+
 #define OFFSET(cfg_entry) ((cfg_entry)->base_offset+(cfg_entry)->field->offset)
 
 /* Add fields to a device - the add_fields macro expects to get a pointer to
diff --git a/drivers/xen/xen-pciback/conf_space_header.c b/drivers/xen/xen-pciback/conf_space_header.c
index c5ee82587e8c..2d7369391472 100644
--- a/drivers/xen/xen-pciback/conf_space_header.c
+++ b/drivers/xen/xen-pciback/conf_space_header.c
@@ -11,6 +11,10 @@
 #include "pciback.h"
 #include "conf_space.h"
 
+struct pci_cmd_info {
+        u16 val;
+};
+
 struct pci_bar_info {
         u32 val;
         u32 len_val;
@@ -20,22 +24,36 @@ struct pci_bar_info {
 #define is_enable_cmd(value) ((value)&(PCI_COMMAND_MEMORY|PCI_COMMAND_IO))
 #define is_master_cmd(value) ((value)&PCI_COMMAND_MASTER)
 
-static int command_read(struct pci_dev *dev, int offset, u16 *value, void *data)
+/* Bits guests are allowed to control in permissive mode. */
+#define PCI_COMMAND_GUEST (PCI_COMMAND_MASTER|PCI_COMMAND_SPECIAL| \
+                           PCI_COMMAND_INVALIDATE|PCI_COMMAND_VGA_PALETTE| \
+                           PCI_COMMAND_WAIT|PCI_COMMAND_FAST_BACK)
+
+static void *command_init(struct pci_dev *dev, int offset)
 {
-        int i;
-        int ret;
-
-        ret = xen_pcibk_read_config_word(dev, offset, value, data);
-        if (!pci_is_enabled(dev))
-                return ret;
-
-        for (i = 0; i < PCI_ROM_RESOURCE; i++) {
-                if (dev->resource[i].flags & IORESOURCE_IO)
-                        *value |= PCI_COMMAND_IO;
-                if (dev->resource[i].flags & IORESOURCE_MEM)
-                        *value |= PCI_COMMAND_MEMORY;
+        struct pci_cmd_info *cmd = kmalloc(sizeof(*cmd), GFP_KERNEL);
+        int err;
+
+        if (!cmd)
+                return ERR_PTR(-ENOMEM);
+
+        err = pci_read_config_word(dev, PCI_COMMAND, &cmd->val);
+        if (err) {
+                kfree(cmd);
+                return ERR_PTR(err);
         }
 
+        return cmd;
+}
+
+static int command_read(struct pci_dev *dev, int offset, u16 *value, void *data)
+{
+        int ret = pci_read_config_word(dev, offset, value);
+        const struct pci_cmd_info *cmd = data;
+
+        *value &= PCI_COMMAND_GUEST;
+        *value |= cmd->val & ~PCI_COMMAND_GUEST;
+
         return ret;
 }
 
@@ -43,6 +61,8 @@ static int command_write(struct pci_dev *dev, int offset, u16 value, void *data)
 {
         struct xen_pcibk_dev_data *dev_data;
         int err;
+        u16 val;
+        struct pci_cmd_info *cmd = data;
 
         dev_data = pci_get_drvdata(dev);
         if (!pci_is_enabled(dev) && is_enable_cmd(value)) {
@@ -83,6 +103,19 @@ static int command_write(struct pci_dev *dev, int offset, u16 value, void *data)
                 }
         }
 
+        cmd->val = value;
+
+        if (!permissive && (!dev_data || !dev_data->permissive))
+                return 0;
+
+        /* Only allow the guest to control certain bits. */
+        err = pci_read_config_word(dev, offset, &val);
+        if (err || val == value)
+                return err;
+
+        value &= PCI_COMMAND_GUEST;
+        value |= val & ~PCI_COMMAND_GUEST;
+
         return pci_write_config_word(dev, offset, value);
 }
 
@@ -282,6 +315,8 @@ static const struct config_field header_common[] = {
         {
          .offset    = PCI_COMMAND,
          .size      = 2,
+         .init      = command_init,
+         .release   = bar_release,
          .u.w.read  = command_read,
          .u.w.write = command_write,
         },