Commit 5b5f1460 authored Sep 04, 2019 by Alexander Duyck Committed by Greg Kroah-Hartman Sep 19, 2019

ixgbe: Prevent u8 wrapping of ITR value to something less than 10us



commit 377228accbbb8b9738f615d791aa803f41c067e0 upstream.

There were a couple cases where the ITR value generated via the adaptive
ITR scheme could exceed 126. This resulted in the value becoming either 0
or something less than 10. Switching back and forth between a value less
than 10 and a value greater than 10 can cause issues as certain hardware
features such as RSC to not function well when the ITR value has dropped
that low.

CC: stable@vger.kernel.org
Fixes: b4ded832 ("ixgbe: Update adaptive ITR algorithm")
Reported-by: Gregg Leventhal <gleventhal@janestreet.com>
Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 7cbd49cf

drivers/net/ethernet/intel/ixgbe/ixgbe_main.c

+3 −1

Original line number	Diff line number	Diff line
		@@ -2626,7 +2626,7 @@ static void ixgbe_update_itr(struct ixgbe_q_vector *q_vector,
		/* 16K ints/sec to 9.2K ints/sec */
		avg_wire_size *= 15;
		avg_wire_size += 11452;
		} else if (avg_wire_size <= 1980) {
		} else if (avg_wire_size < 1968) {
		/* 9.2K ints/sec to 8K ints/sec */
		avg_wire_size *= 5;
		avg_wire_size += 22420;
		@@ -2659,6 +2659,8 @@ static void ixgbe_update_itr(struct ixgbe_q_vector *q_vector,
		case IXGBE_LINK_SPEED_2_5GB_FULL:
		case IXGBE_LINK_SPEED_1GB_FULL:
		case IXGBE_LINK_SPEED_10_FULL:
		if (avg_wire_size > 8064)
		avg_wire_size = 8064;
		itr += DIV_ROUND_UP(avg_wire_size,
		IXGBE_ITR_ADAPTIVE_MIN_INC * 64) *
		IXGBE_ITR_ADAPTIVE_MIN_INC;