netdev - [PATCH net 3/4] bnxt_en: Fix counter overflow logic.

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Message-Id: <1605486472-28156-4-git-send-email-michael.chan@broadcom.com>
Date:   Sun, 15 Nov 2020 19:27:51 -0500
From:   Michael Chan <michael.chan@...adcom.com>
To:     kuba@...nel.org
Cc:     netdev@...r.kernel.org, gospo@...adcom.com
Subject: [PATCH net 3/4] bnxt_en: Fix counter overflow logic.

bnxt_add_one_ctr() adds a hardware counter to a software counter and
adjusts for the hardware counter wraparound against the mask.  The logic
assumes that the hardware counter is always smaller than or equal to
the mask.

This assumption is mostly correct.  But in some cases if the firmware
is older and does not provide the accurate mask, the driver can use
a mask that is smaller than the actual hardware mask.  This can cause
some extra carry bits to be added to the software counter, resulting in
counters that far exceed the actual value.  Fix it by masking the
hardware counter with the mask passed into bnxt_add_one_ctr().

Fixes: fea6b3335527 ("bnxt_en: Accumulate all counters.")
Reviewed-by: Vasundhara Volam <vasundhara-v.volam@...adcom.com>
Reviewed-by: Pavan Chebbi <pavan.chebbi@...adcom.com>
Reviewed-by: Edwin Peer <edwin.peer@...adcom.com>
Signed-off-by: Michael Chan <michael.chan@...adcom.com>
---
 drivers/net/ethernet/broadcom/bnxt/bnxt.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.c b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
index 448e1ba762ee..7c21aaa8b9af 100644
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt.c
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
@@ -7758,6 +7758,7 @@ static void bnxt_add_one_ctr(u64 hw, u64 *sw, u64 mask)
 {
 	u64 sw_tmp;

+	hw &= mask;
 	sw_tmp = (*sw & ~mask) | hw;
 	if (hw < (*sw & mask))
 		sw_tmp += mask + 1;
-- 
2.18.1

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