vfio/migration: Fix incorrect reporting for VFIO pending data

VFIO reports different things in its fast/slow version of query pending
results.  It was because it wants to make sure precopy data can reach 0,
which is needed to make sure sync queries will happen periodically over
time.

Now with stopcopy size reporting facility it doesn't need this hack
anymore.  Fix this by reporting the same values in fast/slow versions of
query pending request, except that the slow version will do a slow sync
with the hardwares.

When at it, removing the special casing for vfio_device_state_is_precopy()
which may reporting nothing in a fast query.  Then ther reporting will be
consistent to VFIO devices that do not support precopy phase.

Copy stable might be too much; just skip it and skip the Fixes.

Reviewed-by: Avihai Horon <avihaih@nvidia.com>
Tested-by: Avihai Horon <avihaih@nvidia.com>
Link: https://lore.kernel.org/r/20260421202110.306051-9-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>

diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c
index e965ba51fbab9844810f656d2a8ccffde6f3e9c0..e6e6a0d53d4bcc5c55b72aacdd85df696c2a3f92 100644 (file)
--- a/hw/vfio/migration.c
+++ b/hw/vfio/migration.c
@@ -587,19 +587,23 @@ static void vfio_state_pending(void *opaque, MigPendingData *pending,
 {
     VFIODevice *vbasedev = opaque;
     VFIOMigration *migration = vbasedev->migration;
-    uint64_t remain;
+    uint64_t precopy_size, stopcopy_size;
 
     if (exact) {
         vfio_state_pending_sync(vbasedev);
-        remain = migration->stopcopy_size;
+    }
+
+    precopy_size =
+        migration->precopy_init_size + migration->precopy_dirty_size;
+
+    if (migration->stopcopy_size > precopy_size) {
+        stopcopy_size = migration->stopcopy_size - precopy_size;
     } else {
-        if (!vfio_device_state_is_precopy(vbasedev)) {
-            return;
-        }
-        remain = migration->precopy_init_size + migration->precopy_dirty_size;
+        stopcopy_size = 0;
     }
 
-    pending->precopy_bytes += remain;
+    pending->precopy_bytes += precopy_size;
+    pending->stopcopy_bytes += stopcopy_size;
 
     trace_vfio_state_pending(vbasedev->name, migration->stopcopy_size,
                              migration->precopy_init_size,