[PATCH v20210713 25/31] tools: add callback to libxl for precopy_policy and precopy_stats

[Olaf Hering <olaf@aepfle.de>]

This duplicates simple_precopy_policy. To recap its purpose:
- do up to 5 iterations of copying dirty domU memory to target,
  including the initial copying of all domU memory, excluding
  the final copying while the domU is suspended
- do fewer iterations in case the domU dirtied less than 50 pages

Take the opportunity to also move xen_pfn_t into qw().

Signed-off-by: Olaf Hering <olaf@aepfle.de>
---
v02:
- use plain struct precopy_stats instead of inventing
  a new precopy_stats_t (anthony)
---
 tools/libs/light/libxl_dom_save.c       | 19 +++++++++++++++++++
 tools/libs/light/libxl_internal.h       |  2 ++
 tools/libs/light/libxl_save_msgs_gen.pl |  3 ++-
 3 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/tools/libs/light/libxl_dom_save.c b/tools/libs/light/libxl_dom_save.c
index 32e3cb5a13..839e061881 100644
--- a/tools/libs/light/libxl_dom_save.c
+++ b/tools/libs/light/libxl_dom_save.c
@@ -373,6 +373,24 @@ int libxl__save_emulator_xenstore_data(libxl__domain_save_state *dss,
     return rc;
 }
 
+static int libxl__domain_save_precopy_policy(struct precopy_stats stats, void *user)
+{
+    libxl__save_helper_state *shs = user;
+    libxl__domain_save_state *dss = shs->caller_state;
+    STATE_AO_GC(dss->ao);
+
+    LOGD(DEBUG, shs->domid, "iteration %u dirty_count %ld total_written %lu",
+         stats.iteration, stats.dirty_count, stats.total_written);
+    if (stats.dirty_count >= 0 && stats.dirty_count < LIBXL_XGS_POLICY_TARGET_DIRTY_COUNT)
+        goto stop_copy;
+    if (stats.iteration >= LIBXL_XGS_POLICY_MAX_ITERATIONS)
+        goto stop_copy;
+    return XGS_POLICY_CONTINUE_PRECOPY;
+
+stop_copy:
+    return XGS_POLICY_STOP_AND_COPY;
+}
+
 /*----- main code for saving, in order of execution -----*/
 
 void libxl__domain_save(libxl__egc *egc, libxl__domain_save_state *dss)
@@ -430,6 +448,7 @@ void libxl__domain_save(libxl__egc *egc, libxl__domain_save_state *dss)
         callbacks->suspend = libxl__domain_suspend_callback;
 
     callbacks->switch_qemu_logdirty = libxl__domain_suspend_common_switch_qemu_logdirty;
+    callbacks->precopy_policy = libxl__domain_save_precopy_policy;
 
     dss->sws.ao  = dss->ao;
     dss->sws.dss = dss;
diff --git a/tools/libs/light/libxl_internal.h b/tools/libs/light/libxl_internal.h
index 0b4671318c..f7df4ab397 100644
--- a/tools/libs/light/libxl_internal.h
+++ b/tools/libs/light/libxl_internal.h
@@ -124,6 +124,8 @@
 #define DOMID_XS_PATH "domid"
 #define PVSHIM_BASENAME "xen-shim"
 #define PVSHIM_CMDLINE "pv-shim console=xen,pv"
+#define LIBXL_XGS_POLICY_MAX_ITERATIONS 5
+#define LIBXL_XGS_POLICY_TARGET_DIRTY_COUNT 50
 
 /* Size macros. */
 #define __AC(X,Y)   (X##Y)
diff --git a/tools/libs/light/libxl_save_msgs_gen.pl b/tools/libs/light/libxl_save_msgs_gen.pl
index 9d425b1dee..b95942ed91 100755
--- a/tools/libs/light/libxl_save_msgs_gen.pl
+++ b/tools/libs/light/libxl_save_msgs_gen.pl
@@ -23,6 +23,7 @@ our @msgs = (
                                              STRING doing_what),
                                             'unsigned long', 'done',
                                             'unsigned long', 'total'] ],
+    [ 'scxW',   "precopy_policy", ['struct precopy_stats', 'stats'] ],
     [ 'srcxA',  "suspend", [] ],
     [ 'srcxA',  "postcopy", [] ],
     [ 'srcxA',  "checkpoint", [] ],
@@ -142,7 +143,7 @@ static void bytes_put(unsigned char *const buf, int *len,
 
 END
 
-foreach my $simpletype (qw(int uint16_t uint32_t unsigned), 'unsigned long', 'xen_pfn_t') {
+foreach my $simpletype (qw(int uint16_t uint32_t unsigned xen_pfn_t), 'struct precopy_stats', 'unsigned long') {
     my $typeid = typeid($simpletype);
     $out_body{'callout'} .= <<END;
 static int ${typeid}_get(const unsigned char **msg,