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/*
* This file is subject to the terms and conditions of the GNU General
* Public License. See the file "COPYING" in the main directory of
* this archive for more details.
*
* Copyright (C) 2005 by Christian Limpach
*
*/
#include <err.h>
#include <stdlib.h>
#include <stdint.h>
#include <string.h>
#include <stdio.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <err.h>
#include <xs.h>
#include <xenctrl.h>
#include <xenguest.h>
/**
* Issue a suspend request through stdout, and receive the acknowledgement
* from stdin. This is handled by XendCheckpoint in the Python layer.
*/
static int suspend(int domid)
{
char ans[30];
printf("suspend\n");
fflush(stdout);
return (fgets(ans, sizeof(ans), stdin) != NULL &&
!strncmp(ans, "done\n", 5));
}
/* For HVM guests, there are two sources of dirty pages: the Xen shadow
* log-dirty bitmap, which we get with a hypercall, and qemu's version.
* The protocol for getting page-dirtying data from qemu uses a
* double-buffered shared memory interface directly between xc_save and
* qemu-dm.
*
* xc_save calculates the size of the bitmaps and notifies qemu-dm
* through the store that it wants to share the bitmaps. qemu-dm then
* starts filling in the 'active' buffer.
*
* To change the buffers over, xc_save writes the other buffer number to
* the store and waits for qemu to acknowledge that it is now writing to
* the new active buffer. xc_save can then process and clear the old
* active buffer. */
static char *qemu_active_path;
static char *qemu_next_active_path;
static int qemu_shmid = -1;
static struct xs_handle *xs;
/* Mark the shared-memory segment for destruction */
static void qemu_destroy_buffer(void)
{
if (qemu_shmid != -1)
shmctl(qemu_shmid, IPC_RMID, NULL);
qemu_shmid = -1;
}
/* Get qemu to change buffers. */
static void qemu_flip_buffer(int domid, int next_active)
{
char digit = '0' + next_active;
unsigned int len;
char *active_str, **watch;
struct timeval tv;
fd_set fdset;
/* Tell qemu that we want it to start writing log-dirty bits to the
* other buffer */
if (!xs_write(xs, XBT_NULL, qemu_next_active_path, &digit, 1)) {
errx(1, "can't write next-active to store path (%s)\n",
qemu_next_active_path);
exit(1);
}
/* Wait a while for qemu to signal that it has switched to the new
* active buffer */
read_again:
tv.tv_sec = 5;
tv.tv_usec = 0;
FD_ZERO(&fdset);
FD_SET(xs_fileno(xs), &fdset);
if ((select(xs_fileno(xs) + 1, &fdset, NULL, NULL, &tv)) != 1) {
errx(1, "timed out waiting for qemu to switch buffers\n");
exit(1);
}
watch = xs_read_watch(xs, &len);
free(watch);
active_str = xs_read(xs, XBT_NULL, qemu_active_path, &len);
if (active_str == NULL || active_str[0] - '0' != next_active)
/* Watch fired but value is not yet right */
goto read_again;
}
static void * init_qemu_maps(int domid, unsigned int bitmap_size)
{
key_t key;
char key_ascii[17] = {0,};
void *seg;
char *path, *p;
/* Make a shared-memory segment */
do {
key = rand(); /* No security, just a sequence of numbers */
qemu_shmid = shmget(key, 2 * bitmap_size,
IPC_CREAT|IPC_EXCL|S_IRUSR|S_IWUSR);
if (qemu_shmid == -1 && errno != EEXIST)
errx(1, "can't get shmem to talk to qemu-dm");
} while (qemu_shmid == -1);
/* Remember to tidy up after ourselves */
atexit(qemu_destroy_buffer);
/* Map it into our address space */
seg = shmat(qemu_shmid, NULL, 0);
if (seg == (void *) -1)
errx(1, "can't map shmem to talk to qemu-dm");
memset(seg, 0, 2 * bitmap_size);
/* Write the size of it into the first 32 bits */
*(uint32_t *)seg = bitmap_size;
/* Tell qemu about it */
if ((xs = xs_daemon_open()) == NULL)
errx(1, "Couldn't contact xenstore");
if (!(path = strdup("/local/domain/0/device-model/")))
errx(1, "can't get domain path in store");
if (!(path = realloc(path, strlen(path)
+ 10
+ strlen("/logdirty/next-active") + 1)))
errx(1, "no memory for constructing xenstore path");
snprintf(path + strlen(path), 11, "%i", domid);
strcat(path, "/logdirty/");
p = path + strlen(path);
strcpy(p, "key");
snprintf(key_ascii, 17, "%16.16llx", (unsigned long long) key);
if (!xs_write(xs, XBT_NULL, path, key_ascii, 16))
errx(1, "can't write key (%s) to store path (%s)\n", key_ascii, path);
/* Watch for qemu's indication of the active buffer, and request it
* to start writing to buffer 0 */
strcpy(p, "active");
if (!xs_watch(xs, path, "qemu-active-buffer"))
errx(1, "can't set watch in store (%s)\n", path);
if (!(qemu_active_path = strdup(path)))
errx(1, "no memory for copying xenstore path");
strcpy(p, "next-active");
if (!(qemu_next_active_path = strdup(path)))
errx(1, "no memory for copying xenstore path");
qemu_flip_buffer(domid, 0);
free(path);
return seg;
}
int
main(int argc, char **argv)
{
unsigned int xc_fd, io_fd, domid, maxit, max_f, flags;
int ret;
if (argc != 6)
errx(1, "usage: %s iofd domid maxit maxf flags", argv[0]);
xc_fd = xc_interface_open();
if (xc_fd < 0)
errx(1, "failed to open control interface");
io_fd = atoi(argv[1]);
domid = atoi(argv[2]);
maxit = atoi(argv[3]);
max_f = atoi(argv[4]);
flags = atoi(argv[5]);
ret = xc_domain_save(xc_fd, io_fd, domid, maxit, max_f, flags,
&suspend, !!(flags & XCFLAGS_HVM),
&init_qemu_maps, &qemu_flip_buffer);
xc_interface_close(xc_fd);
return ret;
}
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