[xen staging] libxl: require qemu in dom0 for multiple stubdomain consoles

[patchbot@xxxxxxx]

commit ab9ce23f5af8f77078d63b11ff8bd7280e0e6b50
Author:     Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
AuthorDate: Mon May 18 21:54:59 2020 -0400
Commit:     Wei Liu <wl@xxxxxxx>
CommitDate: Tue May 19 16:19:15 2020 +0100

    libxl: require qemu in dom0 for multiple stubdomain consoles
    
    Device model stubdomains (both Mini-OS + qemu-trad and linux + qemu-xen)
    are always started with at least 3 consoles: log, save, and restore.
    Until xenconsoled learns how to handle multiple consoles, this is needed
    for save/restore support.
    
    For Mini-OS stubdoms, this is a bug.  In practice, it works in most
    cases because there is something else that triggers qemu in dom0 too:
    vfb/vkb added if vnc/sdl/spice is enabled.
    
    Additionally, Linux-based stubdomain waits for all the backends to
    initialize during boot. Lack of some console backends results in
    stubdomain startup timeout.
    
    This is a temporary patch until xenconsoled will be improved.
    
    Signed-off-by: Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
    [Updated commit message with Marek's explanation from mailing list.]
    Signed-off-by: Jason Andryuk <jandryuk@xxxxxxxxx>
    Acked-by: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
---
 tools/libxl/libxl_dm.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/tools/libxl/libxl_dm.c b/tools/libxl/libxl_dm.c
index 6a26634ef9..8801e9364e 100644
--- a/tools/libxl/libxl_dm.c
+++ b/tools/libxl/libxl_dm.c
@@ -2494,7 +2494,11 @@ static void spawn_stub_launch_dm(libxl__egc *egc,
         }
     }
 
-    need_qemu = libxl__need_xenpv_qemu(gc, dm_config);
+    /*
+     * Until xenconsoled learns how to handle multiple consoles, require qemu
+     * in dom0 to serve consoles for a stubdomain - it require at least 3 of 
them.
+     */
+    need_qemu = 1 || libxl__need_xenpv_qemu(gc, &sdss->dm_config);
 
     for (i = 0; i < num_console; i++) {
         libxl__device device;
@@ -2626,7 +2630,11 @@ static void qmp_proxy_spawn_outcome(libxl__egc *egc,
                                     int rc)
 {
     STATE_AO_GC(sdss->qmp_proxy_spawn.ao);
-    int need_pvqemu = libxl__need_xenpv_qemu(gc, &sdss->dm_config);
+    /*
+     * Until xenconsoled learns how to handle multiple consoles, require qemu
+     * in dom0 to serve consoles for a stubdomain - it require at least 3 of 
them.
+     */
+    int need_pvqemu = 1 || libxl__need_xenpv_qemu(gc, &sdss->dm_config);
 
     if (rc) goto out;
 
--
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