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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH v3 30/31] libxl_dm: Pre-open QMP socket for QEMU
When starting QEMU with dm_restrict=1, pre-open the QMP socket before
exec QEMU. That socket will be usefull to findout if QEMU is ready, and
pre-opening it means that libxl can connect to it without waiting for
QEMU to create it.
The pre-openning is conditionnal, based on the use of dm_restrict
because it is using a new command line option of QEMU, and dm_restrict
support in QEMU is newer.
-chardev socket,fd=X is available with QEMU 2.12, since commit:
> char: allow passing pre-opened socket file descriptor at startup
> 0935700f8544033ebbd41e1f13cd528f8a58d24d
dm_restrict will be available in QEMU 3.0.
Signed-off-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>
---
Notes:
We may want to set cloexec on the socket up to the forking point. Because if
the socket stay open in a random process, libxl will not detected right
away if
QEMU as failed to start. On the other hand, we can rely on timeouts.
tools/libxl/libxl_dm.c | 73 ++++++++++++++++++++++++++++++++++++------
1 file changed, 64 insertions(+), 9 deletions(-)
diff --git a/tools/libxl/libxl_dm.c b/tools/libxl/libxl_dm.c
index 18ada69e8b..10b35d822a 100644
--- a/tools/libxl/libxl_dm.c
+++ b/tools/libxl/libxl_dm.c
@@ -24,6 +24,8 @@
#include <sys/types.h>
#include <pwd.h>
#include <grp.h>
+#include <sys/socket.h>
+#include <sys/un.h>
static const char *libxl_tapif_script(libxl__gc *gc)
{
@@ -913,7 +915,7 @@ static int libxl__build_device_model_args_new(libxl__gc *gc,
const libxl_domain_config
*guest_config,
char ***args, char ***envs,
const libxl__domain_build_state *state,
- int *dm_state_fd)
+ int *dm_state_fd, int *dm_monitor_fd)
{
const libxl_domain_create_info *c_info = &guest_config->c_info;
const libxl_domain_build_info *b_info = &guest_config->b_info;
@@ -942,10 +944,58 @@ static int libxl__build_device_model_args_new(libxl__gc
*gc,
GCSPRINTF("%d", guest_domid), NULL);
flexarray_append(dm_args, "-chardev");
- flexarray_append(dm_args,
- GCSPRINTF("socket,id=libxl-cmd,"
- "path=%s/qmp-libxl-%d,server,nowait",
- libxl__run_dir_path(), guest_domid));
+ /* If we have to use dm_restrict, QEMU need to be new enough and will have
+ * the new interface where we can pre-open the QMP socket. */
+ if (libxl_defbool_val(b_info->dm_restrict))
+ {
+ int socket_fd = -1;
+ struct sockaddr_un un;
+ const char *socket_path;
+
+ socket_fd = socket(AF_UNIX, SOCK_STREAM, 0);
+ *dm_monitor_fd = socket_fd;
+ if (socket_fd < 0) {
+ LOGED(ERROR, guest_domid, "Failed to create UNIX socket");
+ return ERROR_FAIL;
+ }
+
+ socket_path = GCSPRINTF("%s/qmp-libxl-%d",
+ libxl__run_dir_path(), guest_domid);
+ if (strlen(socket_path) > sizeof(un.sun_path)) {
+ LOGD(ERROR, guest_domid, "UNIX socket path '%s' is too long",
+ socket_path);
+ LOGD(DEBUG, guest_domid, "Path must be less than %zu bytes",
+ sizeof(un.sun_path));
+ return ERROR_FAIL;
+ }
+
+ if (unlink(socket_path) < 0 && errno != ENOENT) {
+ LOGED(ERROR, guest_domid, "Failed to unlink socket %s",
socket_path);
+ return ERROR_FAIL;
+ }
+
+ memset(&un, 0, sizeof(un));
+ un.sun_family = AF_UNIX;
+ strncpy(un.sun_path, socket_path, sizeof(un.sun_path));
+ if (bind(socket_fd, (struct sockaddr*) &un, sizeof(un)) < 0) {
+ LOGED(ERROR, guest_domid, "Failed to bind socket to %s",
socket_path);
+ return ERROR_FAIL;
+ }
+
+ if (listen(socket_fd, 1) < 0) {
+ LOGED(ERROR, guest_domid, "Failed to listen on socket");
+ return ERROR_FAIL;
+ }
+
+ flexarray_append(dm_args,
+ GCSPRINTF("socket,id=libxl-cmd,fd=%d,server,nowait",
+ socket_fd));
+ } else {
+ flexarray_append(dm_args,
+ GCSPRINTF("socket,id=libxl-cmd,"
+ "path=%s/qmp-libxl-%d,server,nowait",
+ libxl__run_dir_path(), guest_domid));
+ }
flexarray_append(dm_args, "-no-shutdown");
flexarray_append(dm_args, "-mon");
@@ -1722,7 +1772,8 @@ static int libxl__build_device_model_args(libxl__gc *gc,
const libxl_domain_config
*guest_config,
char ***args, char ***envs,
const libxl__domain_build_state *state,
- int *dm_state_fd)
+ int *dm_state_fd,
+ int *dm_monitor_fd)
/* dm_state_fd may be NULL iff caller knows we are using old stubdom
* and therefore will be passing a filename rather than a fd. */
{
@@ -1735,10 +1786,11 @@ static int libxl__build_device_model_args(libxl__gc *gc,
case LIBXL_DEVICE_MODEL_VERSION_QEMU_XEN:
assert(dm_state_fd != NULL);
assert(*dm_state_fd < 0);
+ assert(dm_monitor_fd != NULL);
return libxl__build_device_model_args_new(gc, dm,
guest_domid, guest_config,
args, envs,
- state, dm_state_fd);
+ state, dm_state_fd,
dm_monitor_fd);
default:
LOGED(ERROR, guest_domid, "unknown device model version %d",
guest_config->b_info.device_model_version);
@@ -1958,7 +2010,7 @@ void libxl__spawn_stub_dm(libxl__egc *egc,
libxl__stub_dm_spawn_state *sdss)
ret = libxl__build_device_model_args(gc, "stubdom-dm", guest_domid,
guest_config, &args, NULL,
- d_state, NULL);
+ d_state, NULL, NULL);
if (ret) {
ret = ERROR_FAIL;
goto out;
@@ -2244,6 +2296,7 @@ void libxl__spawn_local_dm(libxl__egc *egc,
libxl__dm_spawn_state *dmss)
char **pass_stuff;
const char *dm;
int dm_state_fd = -1;
+ int dm_monitor_fd = -1;
if (libxl_defbool_val(b_info->device_model_stubdomain)) {
abort();
@@ -2261,7 +2314,8 @@ void libxl__spawn_local_dm(libxl__egc *egc,
libxl__dm_spawn_state *dmss)
}
rc = libxl__build_device_model_args(gc, dm, domid, guest_config,
&args, &envs, state,
- &dm_state_fd);
+ &dm_state_fd,
+ &dm_monitor_fd);
if (rc)
goto out;
@@ -2359,6 +2413,7 @@ out_close:
if (logfile_w >= 0) close(logfile_w);
out:
if (dm_state_fd >= 0) close(dm_state_fd);
+ if (dm_monitor_fd >= 0) close(dm_monitor_fd);
if (rc)
device_model_spawn_outcome(egc, dmss, rc);
}
--
Anthony PERARD
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