migration: fix implicit integer division in migration_update_counters

[PATCH] migration: fix implicit integer division in migration_update_counters

Aadeshveer Singh posted 1 patch 3 weeks ago

Download mbox

Patches applied successfully (tree, apply log)
git fetch https://github.com/patchew-project/qemu tags/patchew/20260316134509.157964-1-aadeshveer07@gmail.com

Maintainers: Peter Xu <peterx@redhat.com>, Fabiano Rosas <farosas@suse.de>

migration/migration.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

Expand all Fold all

[PATCH] migration: fix implicit integer division in migration_update_counters

Posted by Aadeshveer Singh 3 weeks ago

switchover_bw is a uint64_t, so switchover_bw / 1000 results in an
integer division. This value is then assigned to expected_bw_per_ms
which is of type double. This results in losing precision and is type
unsafe. Adding explicit cast ensures floating-point division.

Signed-off-by: Aadeshveer Singh <aadeshveer07@gmail.com>
---
 migration/migration.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/migration/migration.c b/migration/migration.c
index f949708629..7094080285 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -3134,7 +3134,7 @@ static void migration_update_counters(MigrationState *s,
          * If the user specified a switchover bandwidth, let's trust the
          * user so that can be more accurate than what we estimated.
          */
-        expected_bw_per_ms = switchover_bw / 1000;
+        expected_bw_per_ms = (double)switchover_bw / 1000;
     } else {
         /* If the user doesn't specify bandwidth, we use the estimated */
         expected_bw_per_ms = bandwidth;
-- 
2.53.0

Re: [PATCH] migration: fix implicit integer division in migration_update_counters

Posted by Peter Xu 3 weeks ago

On Mon, Mar 16, 2026 at 07:15:09PM +0530, Aadeshveer Singh wrote:
> switchover_bw is a uint64_t, so switchover_bw / 1000 results in an
> integer division. This value is then assigned to expected_bw_per_ms
> which is of type double. This results in losing precision and is type
> unsafe. Adding explicit cast ensures floating-point division.
> 
> Signed-off-by: Aadeshveer Singh <aadeshveer07@gmail.com>

Reviewed-by: Peter Xu <peterx@redhat.com>

Thanks,

> ---
>  migration/migration.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/migration/migration.c b/migration/migration.c
> index f949708629..7094080285 100644
> --- a/migration/migration.c
> +++ b/migration/migration.c
> @@ -3134,7 +3134,7 @@ static void migration_update_counters(MigrationState *s,
>           * If the user specified a switchover bandwidth, let's trust the
>           * user so that can be more accurate than what we estimated.
>           */
> -        expected_bw_per_ms = switchover_bw / 1000;
> +        expected_bw_per_ms = (double)switchover_bw / 1000;
>      } else {
>          /* If the user doesn't specify bandwidth, we use the estimated */
>          expected_bw_per_ms = bandwidth;
> -- 
> 2.53.0
> 

-- 
Peter Xu