[PATCH v4 18/33] migration/multifd: Add multifd_device_state_supported()

[Maciej S. Szmigiero]

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

Since device state transfer via multifd channels requires multifd
channels with packets 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.

Reviewed-by: Fabiano Rosas <faro...@suse.de>
Reviewed-by: Peter Xu <pet...@redhat.com>
Signed-off-by: Maciej S. Szmigiero <maciej.szmigi...@oracle.com>
---
 include/migration/misc.h         | 1 +
 migration/multifd-device-state.c | 7 +++++++
 2 files changed, 8 insertions(+)

diff --git a/include/migration/misc.h b/include/migration/misc.h
index 885022d21a0c..cc987e6e97af 100644
--- a/include/migration/misc.h
+++ b/include/migration/misc.h
@@ -114,5 +114,6 @@ bool migration_block_inactivate(void);
 /* migration/multifd-device-state.c */
 bool multifd_queue_device_state(char *idstr, uint32_t instance_id,
                                 char *data, size_t len);
+bool multifd_device_state_supported(void);
 
 #endif
diff --git a/migration/multifd-device-state.c b/migration/multifd-device-state.c
index d1674b432ff2..cee3c44bcf2a 100644
--- a/migration/multifd-device-state.c
+++ b/migration/multifd-device-state.c
@@ -11,6 +11,7 @@
 #include "qemu/lockable.h"
 #include "migration/misc.h"
 #include "multifd.h"
+#include "options.h"
 
 static QemuMutex queue_job_mutex;
 
@@ -100,3 +101,9 @@ bool multifd_queue_device_state(char *idstr, uint32_t 
instance_id,
 
     return true;
 }
+
+bool multifd_device_state_supported(void)
+{
+    return migrate_multifd() && !migrate_mapped_ram() &&
+        migrate_multifd_compression() == MULTIFD_COMPRESSION_NONE;
+}