[xen staging] libxl_dm: Pre-open QMP socket for QEMU

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[xen staging] libxl_dm: Pre-open QMP socket for QEMU

patchbot
commit 77b595836bfd97711afae9b1bb2548e33e87b042
Author:     Anthony PERARD <[hidden email]>
AuthorDate: Thu May 31 14:43:20 2018 +0100
Commit:     Wei Liu <[hidden email]>
CommitDate: Fri Jan 11 14:57:52 2019 +0000

    libxl_dm: Pre-open QMP socket for QEMU
   
    This patch moves 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 useful to find out if QEMU is ready, and
    pre-opening it means that libxl can connect to it without waiting for
    QEMU to create it.
   
    The pre-opening is conditional, 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 <[hidden email]>
    Acked-by: Ian Jackson <[hidden email]>
---
 tools/libxl/libxl_create.c   |  5 ++++
 tools/libxl/libxl_dm.c       | 71 +++++++++++++++++++++++++++++++++++++++++---
 tools/libxl/libxl_internal.h |  1 +
 3 files changed, 73 insertions(+), 4 deletions(-)

diff --git a/tools/libxl/libxl_create.c b/tools/libxl/libxl_create.c
index 4ca25f56a6..89f4766a27 100644
--- a/tools/libxl/libxl_create.c
+++ b/tools/libxl/libxl_create.c
@@ -763,12 +763,17 @@ static int store_libxl_entry(libxl__gc *gc, uint32_t domid,
 
 void libxl__domain_build_state_init(libxl__domain_build_state *state)
 {
+    state->dm_monitor_fd = -1;
 }
 
 void libxl__domain_build_state_dispose(libxl__domain_build_state *state)
 {
     libxl__file_reference_unmap(&state->pv_kernel);
     libxl__file_reference_unmap(&state->pv_ramdisk);
+    if (state->dm_monitor_fd >= 0) {
+        close(state->dm_monitor_fd);
+        state->dm_monitor_fd = -1;
+    }
 }
 
 /*----- main domain creation -----*/
diff --git a/tools/libxl/libxl_dm.c b/tools/libxl/libxl_dm.c
index 200310083f..b9921eb885 100644
--- a/tools/libxl/libxl_dm.c
+++ b/tools/libxl/libxl_dm.c
@@ -670,6 +670,8 @@ static int libxl__build_device_model_args_old(libxl__gc *gc,
     dm_args = flexarray_make(gc, 16, 1);
     dm_envs = flexarray_make(gc, 16, 1);
 
+    assert(state->dm_monitor_fd == -1);
+
     libxl__set_qemu_env_for_xsa_180(gc, dm_envs);
 
     flexarray_vappend(dm_args, dm,
@@ -1100,6 +1102,51 @@ 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);
+
+    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,
@@ -1132,10 +1179,16 @@ 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");
@@ -2437,6 +2490,16 @@ void libxl__spawn_local_dm(libxl__egc *egc, libxl__dm_spawn_state *dmss)
     if (rc)
         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);
diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
index 3d12748cbb..b50234482c 100644
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -1240,6 +1240,7 @@ typedef struct {
     char *console_tty;
 
     char *saved_state;
+    int dm_monitor_fd;
 
     libxl__file_reference pv_kernel;
     libxl__file_reference pv_ramdisk;
--
generated by git-patchbot for /home/xen/git/xen.git#staging

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