[Xen-devel] [PATCH v8 21/21] libxl: add support for migrating HVM guests without a device model

[Roger Pau Monne <roger.pau@xxxxxxxxxx>]

Only some minor libxl changes are needed in order to be able to migrate HVM
guests without a device model, no hypervisor changes are needed.

This change prevents sending the emulator context if the device model
version is set to none.

Signed-off-by: Roger Pau Monnà <roger.pau@xxxxxxxxxx>
Cc: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
Cc: Ian Campbell <ian.campbell@xxxxxxxxxx>
Cc: Wei Liu <wei.liu2@xxxxxxxxxx>
---
Changes since v7:
 - Prevent sending the emulator context and xenstore record in
   write_emulator_context_record and write_emulator_xenstore_record.
 - Error out if an emulator record is received for a no-dm guest.
---
 tools/libxl/libxl_dom.c          |  3 +++
 tools/libxl/libxl_dom_suspend.c  |  2 ++
 tools/libxl/libxl_stream_read.c  | 16 ++++++++++++++++
 tools/libxl/libxl_stream_write.c | 16 ++++++++++++++++
 4 files changed, 37 insertions(+)

diff --git a/tools/libxl/libxl_dom.c b/tools/libxl/libxl_dom.c
index 037d4dc..685eb25 100644
--- a/tools/libxl/libxl_dom.c
+++ b/tools/libxl/libxl_dom.c
@@ -1315,6 +1315,9 @@ void libxl__domain_suspend_common_switch_qemu_logdirty
     case LIBXL_DEVICE_MODEL_VERSION_QEMU_XEN:
         domain_suspend_switch_qemu_xen_logdirty(domid, enable, shs);
         break;
+    case LIBXL_DEVICE_MODEL_VERSION_NONE:
+        libxl__xc_domain_saverestore_async_callback_done(egc, shs, 0);
+        break;
     default:
         LOG(ERROR,"logdirty switch failed"
             ", no valid device model version found, abandoning suspend");
diff --git a/tools/libxl/libxl_dom_suspend.c b/tools/libxl/libxl_dom_suspend.c
index 4cc01ad..3313ad1 100644
--- a/tools/libxl/libxl_dom_suspend.c
+++ b/tools/libxl/libxl_dom_suspend.c
@@ -43,6 +43,8 @@ int libxl__domain_suspend_device_model(libxl__gc *gc,
         if (ret)
             unlink(filename);
         break;
+    case LIBXL_DEVICE_MODEL_VERSION_NONE:
+        break;
     default:
         return ERROR_INVAL;
     }
diff --git a/tools/libxl/libxl_stream_read.c b/tools/libxl/libxl_stream_read.c
index 4ec29da..258dec4 100644
--- a/tools/libxl/libxl_stream_read.c
+++ b/tools/libxl/libxl_stream_read.c
@@ -539,6 +539,14 @@ static bool process_record(libxl__egc *egc,
         break;
 
     case REC_TYPE_EMULATOR_XENSTORE_DATA:
+        if (dcs->guest_config->b_info.device_model_version ==
+            LIBXL_DEVICE_MODEL_VERSION_NONE) {
+            rc = ERROR_FAIL;
+            LOG(ERROR,
+                "Received a xenstore emulator record when none was expected");
+            goto err;
+        }
+
         if (rec->hdr.length < sizeof(libxl__sr_emulator_hdr)) {
             rc = ERROR_FAIL;
             LOG(ERROR,
@@ -560,6 +568,14 @@ static bool process_record(libxl__egc *egc,
         break;
 
     case REC_TYPE_EMULATOR_CONTEXT:
+        if (dcs->guest_config->b_info.device_model_version ==
+            LIBXL_DEVICE_MODEL_VERSION_NONE) {
+            rc = ERROR_FAIL;
+            LOG(ERROR,
+                "Received an emulator context record when none was expected");
+            goto err;
+        }
+
         write_emulator_blob(egc, stream, rec);
         break;
 
diff --git a/tools/libxl/libxl_stream_write.c b/tools/libxl/libxl_stream_write.c
index 52a60d7..0a6eaf9 100644
--- a/tools/libxl/libxl_stream_write.c
+++ b/tools/libxl/libxl_stream_write.c
@@ -232,6 +232,9 @@ void libxl__stream_write_start(libxl__egc *egc,
             stream->emu_sub_hdr.id = EMULATOR_QEMU_UPSTREAM;
             break;
 
+        case LIBXL_DEVICE_MODEL_VERSION_NONE:
+            break;
+
         default:
             rc = ERROR_FAIL;
             LOG(ERROR, "Unknown emulator for HVM domain");
@@ -359,6 +362,12 @@ static void write_emulator_xenstore_record(libxl__egc *egc,
     char *buf = NULL;
     uint32_t len = 0;
 
+    if (libxl__device_model_version_running(gc, dss->domid) ==
+        LIBXL_DEVICE_MODEL_VERSION_NONE) {
+        emulator_xenstore_record_done(egc, stream);
+        return;
+    }
+
     rc = libxl__save_emulator_xenstore_data(dss, &buf, &len);
     if (rc)
         goto err;
@@ -387,6 +396,7 @@ static void emulator_xenstore_record_done(libxl__egc *egc,
                                           libxl__stream_write_state *stream)
 {
     libxl__domain_suspend_state *dss = stream->dss;
+    STATE_AO_GC(stream->ao);
 
     if (dss->type == LIBXL_DOMAIN_TYPE_HVM)
         write_emulator_context_record(egc, stream);
@@ -410,6 +420,12 @@ static void write_emulator_context_record(libxl__egc *egc,
 
     assert(dss->type == LIBXL_DOMAIN_TYPE_HVM);
 
+    if (libxl__device_model_version_running(gc, dss->domid) ==
+        LIBXL_DEVICE_MODEL_VERSION_NONE) {
+        emulator_context_record_done(egc, stream);
+        return;
+    }
+
     /* Convenience aliases */
     const char *const filename = dss->dm_savefile;
 
-- 
1.9.5 (Apple Git-50.3)


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