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: stable@vger.kernel.org Signed-off-by: Aleksandr Loktionov --- 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