ixgbe_update_itr() packs a mode flag (IXGBE_ITR_ADAPTIVE_LATENCY,
bit 7) and a usecs delay (bits [6:0]) into an unsigned int, then
stores the combined value in ring_container->itr which is declared as
u8. Values above 0xFF wrap on truncation, corrupting both the delay
and the mode flag on the next readback.
Keep the mode bit (IXGBE_ITR_ADAPTIVE_LATENCY) and the usec delay as
separate operands in the final store expression. Clamp only the usecs
portion to [IXGBE_ITR_ADAPTIVE_MIN_USECS, IXGBE_ITR_ADAPTIVE_MAX_USECS]
using clamp_val() so that:
- overflow cannot bleed into the mode bit (bit 7),
- the delay cannot exceed 126 us (IXGBE_ITR_ADAPTIVE_MAX_USECS),
- the delay cannot drop below 10 us (IXGBE_ITR_ADAPTIVE_MIN_USECS).
Fixes: b4ded8327fea ("ixgbe: Update adaptive ITR algorithm")
Cc: [email protected]
Signed-off-by: Aleksandr Loktionov <[email protected]>
Reviewed-by: Simon Horman <[email protected]>
---
v2 -> v3:
- Use clamp_val() instead of min_t() to also guard the lower bound
(IXGBE_ITR_ADAPTIVE_MIN_USECS); keep mode and delay as separate
operands until final store; use IXGBE_ITR_ADAPTIVE_MAX_USECS (126)
as upper bound instead of IXGBE_ITR_ADAPTIVE_LATENCY - 1 (127)
(Simon Horman).
v1 -> v2:
- Add proper [N/M] numbering so patchwork tracks it as part of the set;
no code change.
drivers/net/ethernet/intel/ixgbe/ixgbe_main.c | 10 +++++++---
1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
index 210c7b9..9f3ae21 100644
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
@@ -2886,11 +2886,17 @@ static void ixgbe_update_itr(struct ixgbe_q_vector
*q_vector,
IXGBE_ITR_ADAPTIVE_MIN_INC * 64) *
IXGBE_ITR_ADAPTIVE_MIN_INC;
break;
}
clear_counts:
- /* write back value */
- ring_container->itr = itr;
+ /* Separate mode bit (IXGBE_ITR_ADAPTIVE_LATENCY) from usec delay;
+ * clamp delay to [MIN_USECS, MAX_USECS] before storing to prevent
+ * u8 truncation from corrupting the mode flag or delay on readback.
+ */
+ ring_container->itr = (itr & IXGBE_ITR_ADAPTIVE_LATENCY) |
+ clamp_val(itr & ~IXGBE_ITR_ADAPTIVE_LATENCY,
+ IXGBE_ITR_ADAPTIVE_MIN_USECS,
+ IXGBE_ITR_ADAPTIVE_MAX_USECS);
/* next update should occur within next jiffy */
ring_container->next_update = next_update + 1;
--
2.52.0
