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authorRusty Russell <rusty@rustcorp.com.au>2015-02-13 17:13:43 +1030
committerRusty Russell <rusty@rustcorp.com.au>2015-02-13 17:15:51 +1030
commit55c2d7884e9a97c2f2d46d5818f783bf3dcc5314 (patch)
tree6291c81f9c5456dff1a1c284f8aa14a851f7e5b1
parenttools/lguest: don't start devices until DRIVER_OK status set. (diff)
downloadlinux-dev-55c2d7884e9a97c2f2d46d5818f783bf3dcc5314.tar.xz
linux-dev-55c2d7884e9a97c2f2d46d5818f783bf3dcc5314.zip
lguest: don't look in console features to find emerg_wr.
The 1.0 spec clearly states that you must set the ACKNOWLEDGE and DRIVER status bits before accessing the feature bits. This is a problem for the early console code, which doesn't really want to acknowledge the device (the spec specifically excepts writing to the console's emerg_wr from the usual ordering constrains). Instead, we check that the *size* of the device configuration is sufficient to hold emerg_wr: at worst (if the device doesn't support the VIRTIO_CONSOLE_F_EMERG_WRITE feature), it will ignore the writes. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
-rw-r--r--arch/x86/lguest/boot.c57
1 files changed, 24 insertions, 33 deletions
diff --git a/arch/x86/lguest/boot.c b/arch/x86/lguest/boot.c
index 531b844cb48d..ac4453d8520e 100644
--- 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");
}
/*