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authorMaciej S. Szmigiero <maciej.szmigiero@oracle.com>2025-03-04 23:03:46 +0100
committerCédric Le Goater <clg@redhat.com>2025-03-06 06:47:33 +0100
commitbd846c5d583a63eaaf836403515c4bf3748f3bb3 (patch)
tree19b108fdbf3a9420c0e085432f7d77983a1c6c8f
parent5963c219a0e60d3f20c09ba2d34671d5e9623e70 (diff)
downloadfocaccia-qemu-bd846c5d583a63eaaf836403515c4bf3748f3bb3.tar.gz
focaccia-qemu-bd846c5d583a63eaaf836403515c4bf3748f3bb3.zip
vfio/migration: Convert bytes_transferred counter to atomic
So it can be safety accessed from multiple threads.

This variable type needs to be changed to unsigned long since
32-bit host platforms lack the necessary addition atomics on 64-bit
variables.

Using 32-bit counters on 32-bit host platforms should not be a problem
in practice since they can't realistically address more memory anyway.

Reviewed-by: Cédric Le Goater <clg@redhat.com>
Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>
Link: https://lore.kernel.org/qemu-devel/dc391771d2d9ad0f311994f0cb9e666da564aeaf.1741124640.git.maciej.szmigiero@oracle.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>
-rw-r--r--hw/vfio/migration.c8
1 files changed, 4 insertions, 4 deletions
diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c
index 03890eaa48..5532787be6 100644
--- a/hw/vfio/migration.c
+++ b/hw/vfio/migration.c
@@ -55,7 +55,7 @@
  */
 #define VFIO_MIG_DEFAULT_DATA_BUFFER_SIZE (1 * MiB)
 
-static int64_t bytes_transferred;
+static unsigned long bytes_transferred;
 
 static const char *mig_state_to_str(enum vfio_device_mig_state state)
 {
@@ -391,7 +391,7 @@ static ssize_t vfio_save_block(QEMUFile *f, VFIOMigration *migration)
     qemu_put_be64(f, VFIO_MIG_FLAG_DEV_DATA_STATE);
     qemu_put_be64(f, data_size);
     qemu_put_buffer(f, migration->data_buffer, data_size);
-    bytes_transferred += data_size;
+    qatomic_add(&bytes_transferred, data_size);
 
     trace_vfio_save_block(migration->vbasedev->name, data_size);
 
@@ -1013,12 +1013,12 @@ static int vfio_block_migration(VFIODevice *vbasedev, Error *err, Error **errp)
 
 int64_t vfio_mig_bytes_transferred(void)
 {
-    return bytes_transferred;
+    return MIN(qatomic_read(&bytes_transferred), INT64_MAX);
 }
 
 void vfio_reset_bytes_transferred(void)
 {
-    bytes_transferred = 0;
+    qatomic_set(&bytes_transferred, 0);
 }
 
 /*