linux-kernel - [PATCH 5.15 077/135] bnxt_en: Fix unnecessary dropping of RX packets

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Message-Id: <20220510130742.620644065@linuxfoundation.org>
Date:   Tue, 10 May 2022 15:07:39 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Andy Gospodarek <andrew.gospodarek@...adcom.com>,
        Michael Chan <michael.chan@...adcom.com>,
        Jakub Kicinski <kuba@...nel.org>
Subject: [PATCH 5.15 077/135] bnxt_en: Fix unnecessary dropping of RX packets

From: Michael Chan <michael.chan@...adcom.com>

commit 195af57914d15229186658ed26dab24b9ada4122 upstream.

In bnxt_poll_p5(), we first check cpr->has_more_work.  If it is true,
we are in NAPI polling mode and we will call __bnxt_poll_cqs() to
continue polling.  It is possible to exhanust the budget again when
__bnxt_poll_cqs() returns.

We then enter the main while loop to check for new entries in the NQ.
If we had previously exhausted the NAPI budget, we may call
__bnxt_poll_work() to process an RX entry with zero budget.  This will
cause packets to be dropped unnecessarily, thinking that we are in the
netpoll path.  Fix it by breaking out of the while loop if we need
to process an RX NQ entry with no budget left.  We will then exit
NAPI and stay in polling mode.

Fixes: 389a877a3b20 ("bnxt_en: Process the NQ under NAPI continuous polling.")
Reviewed-by: Andy Gospodarek <andrew.gospodarek@...adcom.com>
Signed-off-by: Michael Chan <michael.chan@...adcom.com>
Signed-off-by: Jakub Kicinski <kuba@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/net/ethernet/broadcom/bnxt/bnxt.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/drivers/net/ethernet/broadcom/bnxt/bnxt.c
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
@@ -2699,6 +2699,10 @@ static int bnxt_poll_p5(struct napi_stru
 			u32 idx = le32_to_cpu(nqcmp->cq_handle_low);
 			struct bnxt_cp_ring_info *cpr2;

+			/* No more budget for RX work */
+			if (budget && work_done >= budget && idx == BNXT_RX_HDL)
+				break;
+
 			cpr2 = cpr->cp_ring_arr[idx];
 			work_done += __bnxt_poll_work(bp, cpr2,
 						      budget - work_done);