hv_netvsc: Fix the TX/RX buffer default sizes

The values were not computed correctly. There are no significant
visible impact, though.

The intended size of RX buffer is 16 MB, and the default slot size is 1728.
So, NETVSC_DEFAULT_RX should be 16*1024*1024 / 1728 = 9709.

The intended size of TX buffer is 1 MB, and the slot size is 6144.
So, NETVSC_DEFAULT_TX should be 1024*1024 / 6144 = 170.

The patch puts the formula directly into the macro, and moves them to
hyperv_net.h, together with related macros.

Fixes: 5023a6db ("netvsc: increase default receive buffer size")
Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/hyperv/hyperv_net.h

@@ -640,13 +640,24 @@ struct nvsp_message {
 /* Max buffer sizes allowed by a host */
 #define NETVSC_RECEIVE_BUFFER_SIZE		(1024 * 1024 * 31) /* 31MB */
 #define NETVSC_RECEIVE_BUFFER_SIZE_LEGACY	(1024 * 1024 * 15) /* 15MB */
+#define NETVSC_RECEIVE_BUFFER_DEFAULT		(1024 * 1024 * 16)
+
 #define NETVSC_SEND_BUFFER_SIZE			(1024 * 1024 * 15)  /* 15MB */
+#define NETVSC_SEND_BUFFER_DEFAULT		(1024 * 1024)
 
 #define NETVSC_INVALID_INDEX			-1
 
 #define NETVSC_SEND_SECTION_SIZE		6144
 #define NETVSC_RECV_SECTION_SIZE		1728
 
+/* Default size of TX buf: 1MB, RX buf: 16MB */
+#define NETVSC_MIN_TX_SECTIONS	10
+#define NETVSC_DEFAULT_TX	(NETVSC_SEND_BUFFER_DEFAULT \
+				 / NETVSC_SEND_SECTION_SIZE)
+#define NETVSC_MIN_RX_SECTIONS	10
+#define NETVSC_DEFAULT_RX	(NETVSC_RECEIVE_BUFFER_DEFAULT \
+				 / NETVSC_RECV_SECTION_SIZE)
+
 #define NETVSC_RECEIVE_BUFFER_ID		0xcafe
 #define NETVSC_SEND_BUFFER_ID			0
 

drivers/net/hyperv/netvsc_drv.c

@@ -47,10 +47,6 @@
 #include "hyperv_net.h"
 
 #define RING_SIZE_MIN		64
-#define NETVSC_MIN_TX_SECTIONS	10
-#define NETVSC_DEFAULT_TX	192	/* ~1M */
-#define NETVSC_MIN_RX_SECTIONS	10	/* ~64K */
-#define NETVSC_DEFAULT_RX	10485   /* Max ~16M */
 
 #define LINKCHANGE_INT (2 * HZ)
 #define VF_TAKEOVER_INT (HZ / 10)