From 85e4ae1e13f54066f031aba3ae71e252dc410c21 Mon Sep 17 00:00:00 2001
From: Sepherosa Ziehau <sephe@FreeBSD.org>
Date: Thu, 1 Dec 2016 03:27:16 +0000
Subject: [PATCH] hyperv/hn: Add HN_DEBUG kernel option.

If bufring is used for per-TX ring descs, don't update "available"
counter, which is only used to help debugging.

MFC after:	1 week
Sponsored by:	Microsoft
Differential Revision:	https://reviews.freebsd.org/D8674
---
 sys/conf/options                   |  2 ++
 sys/dev/hyperv/netvsc/if_hn.c      | 11 +++++++++--
 sys/modules/hyperv/netvsc/Makefile |  2 +-
 3 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/sys/conf/options b/sys/conf/options
index da04567fa48d..289493a55014 100644
--- a/sys/conf/options
+++ b/sys/conf/options
@@ -1001,3 +1001,5 @@ EVDEV_SUPPORT	opt_evdev.h
 EVDEV_DEBUG	opt_evdev.h
 UINPUT_DEBUG	opt_evdev.h
 
+# Hyper-V network driver
+HN_DEBUG	opt_hn.h
diff --git a/sys/dev/hyperv/netvsc/if_hn.c b/sys/dev/hyperv/netvsc/if_hn.c
index f8d296780aff..8e28a4a18c3e 100644
--- a/sys/dev/hyperv/netvsc/if_hn.c
+++ b/sys/dev/hyperv/netvsc/if_hn.c
@@ -57,6 +57,7 @@ __FBSDID("$FreeBSD$");
 
 #include "opt_inet6.h"
 #include "opt_inet.h"
+#include "opt_hn.h"
 
 #include <sys/param.h>
 #include <sys/bus.h>
@@ -1428,10 +1429,12 @@ hn_txdesc_put(struct hn_tx_ring *txr, struct hn_txdesc *txd)
 	txr->hn_txdesc_avail++;
 	SLIST_INSERT_HEAD(&txr->hn_txlist, txd, link);
 	mtx_unlock_spin(&txr->hn_txlist_spin);
-#else
+#else	/* HN_USE_TXDESC_BUFRING */
+#ifdef HN_DEBUG
 	atomic_add_int(&txr->hn_txdesc_avail, 1);
-	buf_ring_enqueue(txr->hn_txdesc_br, txd);
 #endif
+	buf_ring_enqueue(txr->hn_txdesc_br, txd);
+#endif	/* !HN_USE_TXDESC_BUFRING */
 
 	return 1;
 }
@@ -1457,8 +1460,10 @@ hn_txdesc_get(struct hn_tx_ring *txr)
 
 	if (txd != NULL) {
 #ifdef HN_USE_TXDESC_BUFRING
+#ifdef HN_DEBUG
 		atomic_subtract_int(&txr->hn_txdesc_avail, 1);
 #endif
+#endif	/* HN_USE_TXDESC_BUFRING */
 		KASSERT(txd->m == NULL && txd->refs == 0 &&
 		    STAILQ_EMPTY(&txd->agg_list) &&
 		    txd->chim_index == HN_NVS_CHIM_IDX_INVALID &&
@@ -3467,9 +3472,11 @@ hn_tx_ring_create(struct hn_softc *sc, int id)
 		if (txr->hn_tx_sysctl_tree != NULL) {
 			child = SYSCTL_CHILDREN(txr->hn_tx_sysctl_tree);
 
+#ifdef HN_DEBUG
 			SYSCTL_ADD_INT(ctx, child, OID_AUTO, "txdesc_avail",
 			    CTLFLAG_RD, &txr->hn_txdesc_avail, 0,
 			    "# of available TX descs");
+#endif
 #ifdef HN_IFSTART_SUPPORT
 			if (!hn_use_if_start)
 #endif
diff --git a/sys/modules/hyperv/netvsc/Makefile b/sys/modules/hyperv/netvsc/Makefile
index 1d572cb6fef1..ca5f97a5d7ac 100644
--- a/sys/modules/hyperv/netvsc/Makefile
+++ b/sys/modules/hyperv/netvsc/Makefile
@@ -5,7 +5,7 @@
 
 KMOD=	hv_netvsc
 SRCS=	hn_nvs.c hn_rndis.c if_hn.c
-SRCS+=	bus_if.h device_if.h opt_inet.h opt_inet6.h vmbus_if.h
+SRCS+=	bus_if.h device_if.h opt_inet.h opt_inet6.h vmbus_if.h opt_hn.h
 
 CFLAGS+= -I${.CURDIR}/../../../dev/hyperv/netvsc