lguest: support emerg_wr in console device in example launcher.

This is a magic register which causes a character to be outputted: it can
be used even before the device is configured.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

1 files changed, 14 insertions, 3 deletions

diff --git a/tools/lguest/lguest.c b/tools/lguest/lguest.c
index b5ac73525f6d..8959ac246668 100644
--- a/tools/lguest/lguest.c
+++ b/tools/lguest/lguest.c
@@ -71,7 +71,7 @@ typedef uint8_t u8;
 #include "../../include/uapi/linux/virtio_config.h"
 #include "../../include/uapi/linux/virtio_net.h"
 #include "../../include/uapi/linux/virtio_blk.h"
-#include <linux/virtio_console.h>
+#include "../../include/uapi/linux/virtio_console.h"
 #include "../../include/uapi/linux/virtio_rng.h"
 #include <linux/virtio_ring.h>
 #include "../../include/uapi/linux/virtio_pci.h"
@@ -1687,6 +1687,15 @@ static void emulate_mmio_write(struct device *d, u32 off, u32 val, u32 mask)
                 goto write_through16;
         case offsetof(struct virtio_pci_mmio, isr):
                 errx(1, "%s: Unexpected write to isr", d->name);
+        /* Weird corner case: write to emerg_wr of console */
+        case sizeof(struct virtio_pci_mmio)
+                + offsetof(struct virtio_console_config, emerg_wr):
+                if (strcmp(d->name, "console") == 0) {
+                        char c = val;
+                        write(STDOUT_FILENO, &c, 1);
+                        goto write_through32;
+                }
+                /* Fall through... */
         default:
                 errx(1, "%s: Unexpected write to offset %u", d->name, off);
         }
@@ -2048,6 +2057,7 @@ static struct device *new_pci_device(const char *name, u16 type,
 static void setup_console(void)
 {
         struct device *dev;
+        struct virtio_console_config conf;
 
         /* If we can save the initial standard input settings... */
         if (tcgetattr(STDIN_FILENO, &orig_term) == 0) {
@@ -2075,8 +2085,9 @@ static void setup_console(void)
         add_pci_virtqueue(dev, console_input);
         add_pci_virtqueue(dev, console_output);
 
-        /* There's no configuration area for this device. */
-        no_device_config(dev);
+        /* We need a configuration area for the emerg_wr early writes. */
+        add_pci_feature(dev, VIRTIO_CONSOLE_F_EMERG_WRITE);
+        set_device_config(dev, &conf, sizeof(conf));
 
         verbose("device %u: console\n", devices.device_num);
 }