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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>
This commit is contained in:
Rusty Russell 2015-02-11 15:23:01 +10:30
parent b3e28b65de
commit e8330d9bc1
1 changed files with 14 additions and 3 deletions
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17
tools/lguest/lguest.c
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@ -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);
}