[PATCH 04/28] libxl: Invoke libxl__dm_support_*

[Ian Jackson <ian.jackson@eu.citrix.com>]

When creating a domain (including when restoring), invoke the
dm_support_check machinery on the principal qemu dm (if applicable).

This involves another introducing function callback boundary in the
domcreate control flow; but this is a straightforward one.

Now, libxl__dm_supported is available (for the principal qemu dm) in
the rest of the creation path.

No callers of libxl__dm_supported yet.  So in this patch we just
pointlessly run qemu, collect and scan its usage message, and cache
what we understand from the results.

Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
---
v6: New patch.
---
 tools/libxl/libxl_create.c   |   47 ++++++++++++++++++++++++++++++++++--------
 tools/libxl/libxl_internal.h |    1 +
 2 files changed, 39 insertions(+), 9 deletions(-)

diff --git a/tools/libxl/libxl_create.c b/tools/libxl/libxl_create.c
index 261816a..1af7066 100644
--- a/tools/libxl/libxl_create.c
+++ b/tools/libxl/libxl_create.c
@@ -719,6 +719,8 @@ static void remus_checkpoint_stream_done(
  */
 
 /* Event callbacks, in this order: */
+static void domcreate_dm_support_checked(libxl__egc *egc,
+    libxl__dm_support_check_state *checking, int rc);
 static void domcreate_devmodel_started(libxl__egc *egc,
                                        libxl__dm_spawn_state *dmss,
                                        int rc);
@@ -774,7 +776,7 @@ static void initiate_domain_create(libxl__egc *egc,
     /* convenience aliases */
     libxl_domain_config *const d_config = dcs->guest_config;
     libxl__domain_build_state *const state = &dcs->build_state;
-    const int restore_fd = dcs->restore_fd;
+    const libxl_domain_build_info *b_info = &d_config->b_info;
 
     domid = dcs->domid_soft_reset;
 
@@ -911,10 +913,6 @@ static void initiate_domain_create(libxl__egc *egc,
         }
     }
 
-    dcs->bl.ao = ao;
-    libxl_device_disk *bootdisk =
-        d_config->num_disks > 0 ? &d_config->disks[0] : NULL;
-
     /*
      * The devid has to be set before launching the device model. For the
      * hotplug case this is done in libxl_device_nic_add but on domain
@@ -942,6 +940,41 @@ static void initiate_domain_create(libxl__egc *egc,
             d_config->nics[i].devid = ++last_devid;
     }
 
+    if (b_info->type != LIBXL_DOMAIN_TYPE_HVM ||
+        libxl_defbool_val(b_info->device_model_stubdomain)) {
+        domcreate_dm_support_checked(egc, &dcs->dm_support_check, 0);
+    } else {
+        dcs->dm_support_check.ao = ao;
+        dcs->dm_support_check.dm = libxl__domain_device_model(gc, b_info);
+        dcs->dm_support_check.callback = domcreate_dm_support_checked;
+        libxl__dm_support_check_start(&dcs->dm_support_check);
+    }
+
+error_out:
+    assert(ret);
+    domcreate_complete(egc, dcs, ret);
+}
+
+static void domcreate_dm_support_checked(libxl__egc *egc,
+    libxl__dm_support_check_state *checking, int rc)
+{
+    libxl__domain_create_state *dcs =
+        CONTAINER_OF(checking, *dcs, dm_support_check);
+    STATE_AO_GC(dcs->ao);
+    
+    /* convenience aliases */
+    libxl_domain_config *const d_config = dcs->guest_config;
+    const int restore_fd = dcs->restore_fd;
+
+    if (rc) {
+        domcreate_complete(egc, dcs, rc);
+        return;
+    }
+
+    dcs->bl.ao = ao;
+    libxl_device_disk *bootdisk =
+        d_config->num_disks > 0 ? &d_config->disks[0] : NULL;
+
     if (restore_fd >= 0 || dcs->domid_soft_reset != INVALID_DOMID) {
         LOG(DEBUG, "restoring, not running bootloader");
         domcreate_bootloader_done(egc, &dcs->bl, 0);
@@ -959,10 +992,6 @@ static void initiate_domain_create(libxl__egc *egc,
         libxl__bootloader_run(egc, &dcs->bl);
     }
     return;
-
-error_out:
-    assert(ret);
-    domcreate_complete(egc, dcs, ret);
 }
 
 static void domcreate_bootloader_console_available(libxl__egc *egc,
diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
index f963ad6..fd6ef61 100644
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -3510,6 +3510,7 @@ struct libxl__domain_create_state {
     /* private to domain_create */
     int guest_domid;
     libxl__domain_build_state build_state;
+    libxl__dm_support_check_state dm_support_check;
     libxl__bootloader_state bl;
     libxl__stub_dm_spawn_state dmss;
         /* If we're not doing stubdom, we use only dmss.dm,
-- 
1.7.10.4