[PATCH RFC 24/26] migration/multifd: Add migration_has_device_state_support()

[Maciej S. Szmigiero]

From: "Maciej S. Szmigiero" <maciej.szmigiero@oracle.com>

Since device state transfer via multifd channels requires multifd
channels with migration channel header and is currently not compatible
with multifd compression add an appropriate query function so device
can learn whether it can actually make use of it.

Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>
---
 include/migration/misc.h | 1 +
 migration/multifd.c      | 6 ++++++
 2 files changed, 7 insertions(+)

diff --git a/include/migration/misc.h b/include/migration/misc.h
index 25968e31247b..4da4f7f85f18 100644
--- a/include/migration/misc.h
+++ b/include/migration/misc.h
@@ -118,6 +118,7 @@ bool migration_in_bg_snapshot(void);
 void dirty_bitmap_mig_init(void);
 
 /* migration/multifd.c */
+bool migration_has_device_state_support(void);
 int multifd_queue_device_state(char *idstr, uint32_t instance_id,
                                char *data, size_t len);
 
diff --git a/migration/multifd.c b/migration/multifd.c
index d8ce01539a05..d24217e705a0 100644
--- a/migration/multifd.c
+++ b/migration/multifd.c
@@ -819,6 +819,12 @@ bool multifd_queue_page(RAMBlock *block, ram_addr_t offset)
     return multifd_queue_page_locked(block, offset);
 }
 
+bool migration_has_device_state_support(void)
+{
+    return migrate_multifd() && migrate_channel_header() &&
+        migrate_multifd_compression() == MULTIFD_COMPRESSION_NONE;
+}
+
 int multifd_queue_device_state(char *idstr, uint32_t instance_id,
                                char *data, size_t len)
 {