lguest: don't look in console features to find emerg_wr.

[cascardo/linux.git] / arch / x86 / lguest / boot.c

diff --git a/arch/x86/lguest/boot.c b/arch/x86/lguest/boot.c
index 531b844..ac4453d 100644 (file)
--- a/arch/x86/lguest/boot.c
+++ b/arch/x86/lguest/boot.c
@@ -1222,15 +1222,13 @@ static void set_cfg_window(u32 cfg_offset, u32 off)
                         off);
 }
 
-static u32 read_bar_via_cfg(u32 cfg_offset, u32 off)
-{
-       set_cfg_window(cfg_offset, off);
-       return read_pci_config(0, 1, 0,
-                              cfg_offset + sizeof(struct virtio_pci_cap));
-}
-
 static void write_bar_via_cfg(u32 cfg_offset, u32 off, u32 val)
 {
+       /*
+        * We could set this up once, then leave it; nothing else in the *
+        * kernel should touch these registers.  But if it went wrong, that
+        * would be a horrible bug to find.
+        */
        set_cfg_window(cfg_offset, off);
        write_pci_config(0, 1, 0,
                         cfg_offset + sizeof(struct virtio_pci_cap), val);
@@ -1239,8 +1237,9 @@ static void write_bar_via_cfg(u32 cfg_offset, u32 off, u32 val)
 static void probe_pci_console(void)
 {
        u8 cap, common_cap = 0, device_cap = 0;
-       /* Offsets within BAR0 */
-       u32 common_offset, device_offset;
+       /* Offset within BAR0 */
+       u32 device_offset;
+       u32 device_len;
 
        /* Avoid recursive printk into here. */
        console_cfg_offset = -1;
@@ -1263,7 +1262,7 @@ static void probe_pci_console(void)
                u8 vndr = read_pci_config_byte(0, 1, 0, cap);
                if (vndr == PCI_CAP_ID_VNDR) {
                        u8 type, bar;
-                       u32 offset;
+                       u32 offset, length;
 
                        type = read_pci_config_byte(0, 1, 0,
                            cap + offsetof(struct virtio_pci_cap, cfg_type));
@@ -1271,18 +1270,15 @@ static void probe_pci_console(void)
                            cap + offsetof(struct virtio_pci_cap, bar));
                        offset = read_pci_config(0, 1, 0,
                            cap + offsetof(struct virtio_pci_cap, offset));
+                       length = read_pci_config(0, 1, 0,
+                           cap + offsetof(struct virtio_pci_cap, length));
 
                        switch (type) {
-                       case VIRTIO_PCI_CAP_COMMON_CFG:
-                               if (bar == 0) {
-                                       common_cap = cap;
-                                       common_offset = offset;
-                               }
-                               break;
                        case VIRTIO_PCI_CAP_DEVICE_CFG:
                                if (bar == 0) {
                                        device_cap = cap;
                                        device_offset = offset;
+                                       device_len = length;
                                }
                                break;
                        case VIRTIO_PCI_CAP_PCI_CFG:
@@ -1292,32 +1288,27 @@ static void probe_pci_console(void)
                }
                cap = read_pci_config_byte(0, 1, 0, cap + PCI_CAP_LIST_NEXT);
        }
-       if (!common_cap || !device_cap || !console_access_cap) {
+       if (!device_cap || !console_access_cap) {
                printk(KERN_ERR "lguest: No caps (%u/%u/%u) in console!\n",
                       common_cap, device_cap, console_access_cap);
                return;
        }
 
-
-#define write_common_config(reg, val)                                  \
-       write_bar_via_cfg(console_access_cap,                           \
-                         common_offset+offsetof(struct virtio_pci_common_cfg,reg),\
-                         val)
-
-#define read_common_config(reg)                                                \
-       read_bar_via_cfg(console_access_cap,                            \
-                        common_offset+offsetof(struct virtio_pci_common_cfg,reg))
-
-       /* Check features: they must offer EMERG_WRITE */
-       write_common_config(device_feature_select, 0);
-
-       if (!(read_common_config(device_feature)
-             & (1 << VIRTIO_CONSOLE_F_EMERG_WRITE))) {
-               printk(KERN_ERR "lguest: console missing EMERG_WRITE\n");
+       /*
+        * Note that we can't check features, until we've set the DRIVER
+        * status bit.  We don't want to do that until we have a real driver,
+        * so we just check that the device-specific config has room for
+        * emerg_wr.  If it doesn't support VIRTIO_CONSOLE_F_EMERG_WRITE
+        * it should ignore the access.
+        */
+       if (device_len < (offsetof(struct virtio_console_config, emerg_wr)
+                         + sizeof(u32))) {
+               printk(KERN_ERR "lguest: console missing emerg_wr field\n");
                return;
        }
 
        console_cfg_offset = device_offset;
+       printk(KERN_INFO "lguest: Console via virtio-pci emerg_wr\n");
 }
 
 /*