[Qemu-devel] [PATCH v3 2/5] migration: Introduce ignore-shared capability

[Yury Kotov]

We want to use local migration to update QEMU for running guests.
In this case we don't need to migrate shared (file backed) RAM.
So, add a capability to ignore such blocks during live migration.

Signed-off-by: Yury Kotov <address@hidden>
---
 migration/migration.c | 14 ++++++++++++++
 migration/migration.h |  1 +
 qapi/migration.json   |  5 ++++-
 3 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/migration/migration.c b/migration/migration.c
index 37e06b76dc..0fadd97fb9 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -957,6 +957,11 @@ static bool migrate_caps_check(bool *cap_list,
             error_setg(errp, "Postcopy is not supported");
             return false;
         }
+
+        if (cap_list[MIGRATION_CAPABILITY_X_IGNORE_SHARED]) {
+            error_setg(errp, "Postcopy is not compatible with ignore-shared");
+            return false;
+        }
     }
 
     return true;
@@ -1983,6 +1988,15 @@ bool migrate_dirty_bitmaps(void)
     return s->enabled_capabilities[MIGRATION_CAPABILITY_DIRTY_BITMAPS];
 }
 
+bool migrate_ignore_shared(void)
+{
+    MigrationState *s;
+
+    s = migrate_get_current();
+
+    return s->enabled_capabilities[MIGRATION_CAPABILITY_X_IGNORE_SHARED];
+}
+
 bool migrate_use_events(void)
 {
     MigrationState *s;
diff --git a/migration/migration.h b/migration/migration.h
index dcd05d9f87..4211995c53 100644
--- a/migration/migration.h
+++ b/migration/migration.h
@@ -261,6 +261,7 @@ bool migrate_release_ram(void);
 bool migrate_postcopy_ram(void);
 bool migrate_zero_blocks(void);
 bool migrate_dirty_bitmaps(void);
+bool migrate_ignore_shared(void);
 
 bool migrate_auto_converge(void);
 bool migrate_use_multifd(void);
diff --git a/qapi/migration.json b/qapi/migration.json
index 7a795ecc16..7105570cd3 100644
--- a/qapi/migration.json
+++ b/qapi/migration.json
@@ -409,13 +409,16 @@
 #           devices (and thus take locks) immediately at the end of migration.
 #           (since 3.0)
 #
+# @x-ignore-shared: If enabled, QEMU will not migrate shared memory (since 4.0)
+#
 # Since: 1.2
 ##
 { 'enum': 'MigrationCapability',
   'data': ['xbzrle', 'rdma-pin-all', 'auto-converge', 'zero-blocks',
            'compress', 'events', 'postcopy-ram', 'x-colo', 'release-ram',
            'block', 'return-path', 'pause-before-switchover', 'x-multifd',
-           'dirty-bitmaps', 'postcopy-blocktime', 'late-block-activate' ] }
+           'dirty-bitmaps', 'postcopy-blocktime', 'late-block-activate',
+           'x-ignore-shared' ] }
 
 ##
 # @MigrationCapabilityStatus:
-- 
2.20.1