[Xen-devel] [RFC PATCH 07/17] libxl: add save/restore support for qemu-xen in stubdomain

[Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>]

Rely on a wrapper script in stubdomain to attach FD 3/4 of qemu to
relevant consoles.
---
 tools/libxl/libxl_dm.c          | 23 +++++++++++------------
 tools/libxl/libxl_dom_suspend.c | 10 ++++++++--
 2 files changed, 19 insertions(+), 14 deletions(-)

diff --git a/tools/libxl/libxl_dm.c b/tools/libxl/libxl_dm.c
index 7828444..f6bd6a1 100644
--- a/tools/libxl/libxl_dm.c
+++ b/tools/libxl/libxl_dm.c
@@ -1444,10 +1444,17 @@ static int libxl__build_device_model_args_new(libxl__gc 
*gc,
         flexarray_append(dm_args, "-xen-domid-restrict");
 
     if (state->saved_state) {
-        /* This file descriptor is meant to be used by QEMU */
-        *dm_state_fd = open(state->saved_state, O_RDONLY);
-        flexarray_append(dm_args, "-incoming");
-        flexarray_append(dm_args, GCSPRINTF("fd:%d",*dm_state_fd));
+        if (is_stubdom) {
+            /* Linux stubdomain connects specific FD to STUBDOM_CONSOLE_RESTORE
+             */
+            flexarray_append(dm_args, "-incoming");
+            flexarray_append(dm_args, "fd:3");
+        } else {
+            /* This file descriptor is meant to be used by QEMU */
+            *dm_state_fd = open(state->saved_state, O_RDONLY);
+            flexarray_append(dm_args, "-incoming");
+            flexarray_append(dm_args, GCSPRINTF("fd:%d",*dm_state_fd));
+        }
     }
     for (i = 0; b_info->extra && b_info->extra[i] != NULL; i++)
         flexarray_append(dm_args, b_info->extra[i]);
@@ -1929,14 +1936,6 @@ void libxl__spawn_stub_dm(libxl__egc *egc, 
libxl__stub_dm_spawn_state *sdss)
 
     assert(libxl_defbool_val(guest_config->b_info.device_model_stubdomain));
 
-    if (guest_config->b_info.stubdomain_version == 
LIBXL_STUBDOMAIN_VERSION_LINUX) {
-        if (d_state->saved_state) {
-            LOG(ERROR, "Save/Restore not supported yet with Linux Stubdom.");
-            ret = -1;
-            goto out;
-        }
-    }
-
     sdss->pvqemu.guest_domid = 0;
 
     libxl_domain_create_info_init(&dm_config->c_info);
diff --git a/tools/libxl/libxl_dom_suspend.c b/tools/libxl/libxl_dom_suspend.c
index 1e904ba..8c8ae84 100644
--- a/tools/libxl/libxl_dom_suspend.c
+++ b/tools/libxl/libxl_dom_suspend.c
@@ -73,7 +73,8 @@ int libxl__domain_suspend_device_model(libxl__gc *gc,
 {
     int ret = 0;
     uint32_t const domid = dsps->domid;
-    const char *const filename = dsps->dm_savefile;
+    uint32_t dm_domid = libxl_get_stubdom_id(CTX, domid);
+    const char * filename = dsps->dm_savefile;
 
     switch (libxl__device_model_version_running(gc, domid)) {
     case LIBXL_DEVICE_MODEL_VERSION_QEMU_XEN_TRADITIONAL: {
@@ -86,8 +87,13 @@ int libxl__domain_suspend_device_model(libxl__gc *gc,
         if (libxl__qmp_stop(gc, domid))
             return ERROR_FAIL;
         /* Save DM state into filename */
+        if (dm_domid) {
+            /* if DM is in stubdomain, instruct it to use console, which is
+             * connected to a file pointed by filename */
+            filename = "/proc/self/fd/4";
+        }
         ret = libxl__qmp_save(gc, domid, filename, dsps->live);
-        if (ret)
+        if (ret && !dm_domid)
             unlink(filename);
         break;
     default:
-- 
git-series 0.9.1

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