[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

[Xen-devel] [PATCH v6 07/11] libxl_dm: Pre-open QMP socket for QEMU



This patch move the creation of the QMP unix socket from QEMU to libxl.
But libxl doesn't rely on this yet.

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 is available in QEMU 3.0.

Signed-off-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>
---

Notes:
    v6:
        move dm_monitor_fd into libxl_domain_build_info (or d_state)
        -> move the creation of the socket into libxl__spawn_local_dm
           instead of libxl__build_device_model_args
        Use libxl_domid type instead of int for libxl__pre_open_qmp_socket()
        Check function calls (bind and listen) return value in a separate 
statement.
        typo and other coding style issue fixes
    
    v5:
        use libxl__remove_file
        few changes in coding style
        remove stale includes (sys/socket, sys/un) which are now in 
libxl_internal.h
    
    v4:
        separate the logic to open a socket into a function.
        Use libxl__prepare_sockaddr_un() to check path size

 tools/libxl/libxl_create.c   |  3 ++
 tools/libxl/libxl_dm.c       | 71 ++++++++++++++++++++++++++++++++++--
 tools/libxl/libxl_internal.h |  1 +
 3 files changed, 71 insertions(+), 4 deletions(-)

diff --git a/tools/libxl/libxl_create.c b/tools/libxl/libxl_create.c
index fa573344bc..fcbe36feba 100644
--- a/tools/libxl/libxl_create.c
+++ b/tools/libxl/libxl_create.c
@@ -539,6 +539,9 @@ int libxl__domain_make(libxl__gc *gc, libxl_domain_config 
*d_config,
     libxl_domain_create_info *info = &d_config->c_info;
     libxl_domain_build_info *b_info = &d_config->b_info;
 
+    /* Attempt to initialise libxl__domain_build_state */
+    state->dm_monitor_fd = -1;
+
     uuid_string = libxl__uuid2string(gc, info->uuid);
     if (!uuid_string) {
         rc = ERROR_NOMEM;
diff --git a/tools/libxl/libxl_dm.c b/tools/libxl/libxl_dm.c
index 9c47060473..3bf1e37894 100644
--- a/tools/libxl/libxl_dm.c
+++ b/tools/libxl/libxl_dm.c
@@ -910,6 +910,53 @@ static char *qemu_disk_ide_drive_string(libxl__gc *gc, 
const char *target_path,
     return drive;
 }
 
+static int libxl__pre_open_qmp_socket(libxl__gc *gc, libxl_domid domid,
+                                      int *fd_r)
+{
+    int rc, r;
+    int fd;
+    struct sockaddr_un un;
+    const char *path = libxl__qemu_qmp_path(gc, domid);
+
+    assert(fd_r != NULL);
+
+    fd = socket(AF_UNIX, SOCK_STREAM, 0);
+    if (fd < 0) {
+        LOGED(ERROR, domid, "socket() failed");
+        return ERROR_FAIL;
+    }
+
+    rc = libxl__prepare_sockaddr_un(gc, &un, path, "QEMU's QMP socket");
+    if (rc)
+        goto out;
+
+    rc = libxl__remove_file(gc, path);
+    if (rc)
+        goto out;
+
+    r = bind(fd, (struct sockaddr *) &un, sizeof(un));
+    if (r < 0) {
+        LOGED(ERROR, domid, "bind('%s') failed", path);
+        rc = ERROR_FAIL;
+        goto out;
+    }
+
+    r = listen(fd, 1);
+    if (r < 0) {
+        LOGED(ERROR, domid, "listen() failed");
+        rc = ERROR_FAIL;
+        goto out;
+    }
+
+    *fd_r = fd;
+    rc = 0;
+
+out:
+    if (rc && fd >= 0)
+        close(fd);
+    return rc;
+}
+
 static int libxl__build_device_model_args_new(libxl__gc *gc,
                                         const char *dm, int guest_domid,
                                         const libxl_domain_config 
*guest_config,
@@ -944,10 +991,16 @@ 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,server,nowait",
-                               libxl__qemu_qmp_path(gc, guest_domid)));
+    if (state->dm_monitor_fd >= 0) {
+        flexarray_append(dm_args,
+            GCSPRINTF("socket,id=libxl-cmd,fd=%d,server,nowait",
+                      state->dm_monitor_fd));
+    } else {
+        flexarray_append(dm_args,
+                         GCSPRINTF("socket,id=libxl-cmd,"
+                                   "path=%s,server,nowait",
+                                   libxl__qemu_qmp_path(gc, guest_domid)));
+    }
 
     flexarray_append(dm_args, "-no-shutdown");
     flexarray_append(dm_args, "-mon");
@@ -2000,6 +2053,7 @@ void libxl__spawn_stub_dm(libxl__egc *egc, 
libxl__stub_dm_spawn_state *sdss)
     if (ret)
         goto out;
 
+    d_state->dm_monitor_fd = -1;
     ret = libxl__build_device_model_args(gc, "stubdom-dm", guest_domid,
                                          guest_config, &args, NULL,
                                          d_state, NULL);
@@ -2303,6 +2357,14 @@ void libxl__spawn_local_dm(libxl__egc *egc, 
libxl__dm_spawn_state *dmss)
         rc = ERROR_FAIL;
         goto out;
     }
+    if (b_info->device_model_version == LIBXL_DEVICE_MODEL_VERSION_QEMU_XEN &&
+        libxl_defbool_val(b_info->dm_restrict)) {
+        /* If we have to use dm_restrict, QEMU needs to be new enough
+         * and will have the new interface where we can pre-open the
+         * QMP socket. */
+        rc = libxl__pre_open_qmp_socket(gc, domid, &state->dm_monitor_fd);
+        if (rc) goto out;
+    }
     rc = libxl__build_device_model_args(gc, dm, domid, guest_config,
                                           &args, &envs, state,
                                           &dm_state_fd);
@@ -2408,6 +2470,7 @@ out_close:
     if (logfile_w >= 0) close(logfile_w);
 out:
     if (dm_state_fd >= 0) close(dm_state_fd);
+    if (state->dm_monitor_fd >= 0) close(state->dm_monitor_fd);
     if (rc)
         device_model_spawn_outcome(egc, dmss, rc);
 }
diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
index 6c118ccb3b..b768d1b09f 100644
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -1233,6 +1233,7 @@ typedef struct {
     char *console_tty;
 
     char *saved_state;
+    int dm_monitor_fd;
 
     libxl__file_reference pv_kernel;
     libxl__file_reference pv_ramdisk;
-- 
Anthony PERARD


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/xen-devel

 


Rackspace

Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.