Re: [PATCH v3 15/24] migration/multifd: Add migration_has_device_state_support()

[Avihai Horon]

On 17/11/2024 21:20, Maciej S. Szmigiero wrote:
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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.

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 118e205bbcc6..43558d9198f7 100644
--- a/include/migration/misc.h
+++ b/include/migration/misc.h
@@ -112,5 +112,6 @@ bool migration_in_bg_snapshot(void);
  /* migration/multifd-device-state.c */
  bool multifd_queue_device_state(char *idstr, uint32_t instance_id,
                                  char *data, size_t len);
+bool migration_has_device_state_support(void);

Nit: maybe rename to multifd_device_state_supported or 
migration_multifd_device_state_supported, as it's specifically related 
to multifd?

Thanks.


  #endif
diff --git a/migration/multifd-device-state.c b/migration/multifd-device-state.c
index 8cf5a6c2668c..bcbea926b6be 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;

@@ -99,3 +100,9 @@ bool multifd_queue_device_state(char *idstr, uint32_t 
instance_id,

      return true;
  }
+
+bool migration_has_device_state_support(void)
+{
+    return migrate_multifd() && !migrate_mapped_ram() &&
+        migrate_multifd_compression() == MULTIFD_COMPRESSION_NONE;
+}