[PATCH v2 2/2] libxl: do not start dom0 qemu for stubdomain when not needed

["Marek Marczykowski-Górecki" <marmarek@invisiblethingslab.com>]

Do not setup vfb+vkb when no access method was configured. Then check if
qemu is really needed.

The only not configurable thing forcing qemu running in dom0 after this
change are consoles used to save/restore. But even in that case, there
is much smaller part of qemu exposed.

Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
---
 tools/libxl/libxl_dm.c | 54 ++++++++++++++++++++++++++++++++++++--------------
 1 file changed, 39 insertions(+), 15 deletions(-)

diff --git a/tools/libxl/libxl_dm.c b/tools/libxl/libxl_dm.c
index 44ebd70..e0e6a99 100644
--- a/tools/libxl/libxl_dm.c
+++ b/tools/libxl/libxl_dm.c
@@ -1868,13 +1868,17 @@ void libxl__spawn_stub_dm(libxl__egc *egc, libxl__stub_dm_spawn_state *sdss)
     ret = libxl__domain_build_info_setdefault(gc, &dm_config->b_info);
     if (ret) goto out;
 
-    GCNEW(vfb);
-    GCNEW(vkb);
-    libxl__vfb_and_vkb_from_hvm_guest_config(gc, guest_config, vfb, vkb);
-    dm_config->vfbs = vfb;
-    dm_config->num_vfbs = 1;
-    dm_config->vkbs = vkb;
-    dm_config->num_vkbs = 1;
+    if (libxl_defbool_val(guest_config->b_info.u.hvm.vnc.enable)
+        || libxl_defbool_val(guest_config->b_info.u.hvm.spice.enable)
+        || libxl_defbool_val(guest_config->b_info.u.hvm.sdl.enable)) {
+        GCNEW(vfb);
+        GCNEW(vkb);
+        libxl__vfb_and_vkb_from_hvm_guest_config(gc, guest_config, vfb, vkb);
+        dm_config->vfbs = vfb;
+        dm_config->num_vfbs = 1;
+        dm_config->vkbs = vkb;
+        dm_config->num_vkbs = 1;
+    }
 
     stubdom_state->pv_kernel.path
         = libxl__abs_path(gc, "ioemu-stubdom.gz", libxl__xenfirmwaredir_path());
@@ -1959,6 +1963,7 @@ static void spawn_stub_launch_dm(libxl__egc *egc,
     libxl__domain_build_state *const d_state = sdss->dm.build_state;
     libxl__domain_build_state *const stubdom_state = &sdss->dm_state;
     uint32_t dm_domid = sdss->pvqemu.guest_domid;
+    int need_qemu;
 
     if (ret) {
         LOGD(ERROR, guest_domid, "error connecting disk devices");
@@ -1975,12 +1980,16 @@ static void spawn_stub_launch_dm(libxl__egc *egc,
         if (ret)
             goto out;
     }
-    ret = libxl__device_vfb_add(gc, dm_domid, &dm_config->vfbs[0]);
-    if (ret)
-        goto out;
-    ret = libxl__device_vkb_add(gc, dm_domid, &dm_config->vkbs[0]);
-    if (ret)
-        goto out;
+    if (dm_config->num_vfbs) {
+        ret = libxl__device_vfb_add(gc, dm_domid, &dm_config->vfbs[0]);
+        if (ret)
+            goto out;
+    }
+    if (dm_config->num_vkbs) {
+        ret = libxl__device_vkb_add(gc, dm_domid, &dm_config->vkbs[0]);
+        if (ret)
+            goto out;
+    }
 
     if (guest_config->b_info.u.hvm.serial)
         num_console++;
@@ -1988,7 +1997,6 @@ static void spawn_stub_launch_dm(libxl__egc *egc,
     console = libxl__calloc(gc, num_console, sizeof(libxl__device_console));
 
     for (i = 0; i < num_console; i++) {
-        libxl__device device;
         console[i].devid = i;
         console[i].consback = LIBXL__CONSOLE_BACKEND_IOEMU;
         /* STUBDOM_CONSOLE_LOGGING (console 0) is for minios logging
@@ -2005,6 +2013,9 @@ static void spawn_stub_launch_dm(libxl__egc *egc,
                 if (ret) goto out;
                 console[i].output = GCSPRINTF("file:%s", filename);
                 free(filename);
+                /* will be changed back to LIBXL__CONSOLE_BACKEND_IOEMU if qemu
+                 * will be in use */
+                console[i].consback = LIBXL__CONSOLE_BACKEND_XENCONSOLED;
                 break;
             case STUBDOM_CONSOLE_SAVE:
                 console[i].output = GCSPRINTF("file:%s",
@@ -2019,6 +2030,14 @@ static void spawn_stub_launch_dm(libxl__egc *egc,
                 console[i].output = "pty";
                 break;
         }
+    }
+
+    need_qemu = libxl__need_xenpv_qemu(gc, dm_config);
+
+    for (i = 0; i < num_console; i++) {
+        libxl__device device;
+        if (need_qemu)
+            console[i].consback = LIBXL__CONSOLE_BACKEND_IOEMU;
         ret = libxl__device_console_add(gc, dm_domid, &console[i],
                         i == STUBDOM_CONSOLE_LOGGING ? stubdom_state : NULL,
                         &device);
@@ -2032,7 +2051,12 @@ static void spawn_stub_launch_dm(libxl__egc *egc,
     sdss->pvqemu.build_state = &sdss->dm_state;
     sdss->pvqemu.callback = spawn_stubdom_pvqemu_cb;
 
-    libxl__spawn_local_dm(egc, &sdss->pvqemu);
+    if (!need_qemu) {
+        /* If dom0 qemu not needed, do not launch it */
+        spawn_stubdom_pvqemu_cb(egc, &sdss->pvqemu, 0);
+    } else {
+        libxl__spawn_local_dm(egc, &sdss->pvqemu);
+    }
 
     return;
 
-- 
2.7.5


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