diff mbox

[dpdk-dev,2/4] enic: set the max allowed MTU for the NIC

Message ID 1466140969-5580-3-git-send-email-johndale@cisco.com (mailing list archive)
State Superseded, archived
Delegated to: Bruce Richardson
Headers show

Commit Message

John Daley June 17, 2016, 5:22 a.m. UTC
The max MTU is set to the max egress packet size allowed by the VIC
minus the size of a an IPv4 L2 header with .1Q (18 bytes).

Signed-off-by: John Daley <johndale@cisco.com>
---
 drivers/net/enic/enic.h        |  1 +
 drivers/net/enic/enic_ethdev.c |  3 ++-
 drivers/net/enic/enic_res.c    | 25 +++++++++++++++++--------
 drivers/net/enic/enic_res.h    |  4 +++-
 4 files changed, 23 insertions(+), 10 deletions(-)

Comments

Bruce Richardson June 24, 2016, 10:59 a.m. UTC | #1
On Thu, Jun 16, 2016 at 10:22:47PM -0700, John Daley wrote:
> The max MTU is set to the max egress packet size allowed by the VIC
> minus the size of a an IPv4 L2 header with .1Q (18 bytes).
> 

I think a bit more detail might be needed here. For example:

* What was the MTU set to by default before this patch is applied? Was it just
set to 1518 or something else?
* What happens, if anything, if buffers bigger than the MTU size are sent down?

/Bruce
Bruce Richardson June 24, 2016, 11:01 a.m. UTC | #2
On Fri, Jun 24, 2016 at 11:59:19AM +0100, Bruce Richardson wrote:
> On Thu, Jun 16, 2016 at 10:22:47PM -0700, John Daley wrote:
> > The max MTU is set to the max egress packet size allowed by the VIC
> > minus the size of a an IPv4 L2 header with .1Q (18 bytes).
> > 
> 
> I think a bit more detail might be needed here. For example:
> 
> * What was the MTU set to by default before this patch is applied? Was it just
> set to 1518 or something else?
> * What happens, if anything, if buffers bigger than the MTU size are sent down?
This is obviously referring to buffers bigger than MTU on TX. There is also the
question of what happens if buffer sizes smaller than MTU are provided on RX.

> 
> /Bruce
John Daley June 24, 2016, 10:42 p.m. UTC | #3
Hi Bruce,

> > * What was the MTU set to by default before this patch is applied? Was
> > it just set to 1518 or something else?
> > * What happens, if anything, if buffers bigger than the MTU size are sent
> down?
> This is obviously referring to buffers bigger than MTU on TX. There is also the
> question of what happens if buffer sizes smaller than MTU are provided on
> RX.

I think I answered all your questions in the revised commit messages of the v2 patchset (and then some) except this last one. Enic doesn't do any checking on Rx that buffers are greater than the MTU since it would affect performance. However if a packet is bigger than a buffer and Rx scatter is disabled, the packet will be dropped and 'imissed' incremented.

Thanks,
Johnd
diff mbox

Patch

diff --git a/drivers/net/enic/enic.h b/drivers/net/enic/enic.h
index 1e6914e..78f7bd7 100644
--- a/drivers/net/enic/enic.h
+++ b/drivers/net/enic/enic.h
@@ -118,6 +118,7 @@  struct enic {
 	u8 ig_vlan_strip_en;
 	int link_status;
 	u8 hw_ip_checksum;
+	u16 max_mtu;
 
 	unsigned int flags;
 	unsigned int priv_flags;
diff --git a/drivers/net/enic/enic_ethdev.c b/drivers/net/enic/enic_ethdev.c
index 697ff82..31d9600 100644
--- a/drivers/net/enic/enic_ethdev.c
+++ b/drivers/net/enic/enic_ethdev.c
@@ -435,7 +435,8 @@  static void enicpmd_dev_info_get(struct rte_eth_dev *eth_dev,
 	device_info->max_rx_queues = enic->rq_count;
 	device_info->max_tx_queues = enic->wq_count;
 	device_info->min_rx_bufsize = ENIC_MIN_MTU;
-	device_info->max_rx_pktlen = enic->config.mtu;
+	device_info->max_rx_pktlen = enic->rte_dev->data->mtu
+				   + ETHER_HDR_LEN + 4;
 	device_info->max_mac_addrs = 1;
 	device_info->rx_offload_capa =
 		DEV_RX_OFFLOAD_VLAN_STRIP |
diff --git a/drivers/net/enic/enic_res.c b/drivers/net/enic/enic_res.c
index ebe379d..e82181f 100644
--- a/drivers/net/enic/enic_res.c
+++ b/drivers/net/enic/enic_res.c
@@ -83,6 +83,20 @@  int enic_get_vnic_config(struct enic *enic)
 	GET_CONFIG(intr_timer_usec);
 	GET_CONFIG(loop_tag);
 	GET_CONFIG(num_arfs);
+	GET_CONFIG(max_pkt_size);
+
+	/* max packet size is only defined in newer VIC firmware
+	 * and will be 0 for legacy firmware and VICs
+	 */
+	if (c->max_pkt_size > ENIC_DEFAULT_MAX_PKT_SIZE)
+		enic->max_mtu = c->max_pkt_size - (ETHER_HDR_LEN + 4);
+	else
+		enic->max_mtu = ENIC_DEFAULT_MAX_PKT_SIZE - (ETHER_HDR_LEN + 4);
+	if (c->mtu == 0)
+		c->mtu = 1500;
+
+	enic->rte_dev->data->mtu = min_t(u16, enic->max_mtu,
+					 max_t(u16, ENIC_MIN_MTU, c->mtu));
 
 	c->wq_desc_count =
 		min_t(u32, ENIC_MAX_WQ_DESCS,
@@ -96,21 +110,16 @@  int enic_get_vnic_config(struct enic *enic)
 		c->rq_desc_count));
 	c->rq_desc_count &= 0xffffffe0; /* must be aligned to groups of 32 */
 
-	if (c->mtu == 0)
-		c->mtu = 1500;
-	c->mtu = min_t(u16, ENIC_MAX_MTU,
-		max_t(u16, ENIC_MIN_MTU,
-		c->mtu));
-
 	c->intr_timer_usec = min_t(u32, c->intr_timer_usec,
 		vnic_dev_get_intr_coal_timer_max(enic->vdev));
 
 	dev_info(enic_get_dev(enic),
 		"vNIC MAC addr %02x:%02x:%02x:%02x:%02x:%02x "
-		"wq/rq %d/%d mtu %d\n",
+		"wq/rq %d/%d mtu %d, max mtu:%d\n",
 		enic->mac_addr[0], enic->mac_addr[1], enic->mac_addr[2],
 		enic->mac_addr[3], enic->mac_addr[4], enic->mac_addr[5],
-		c->wq_desc_count, c->rq_desc_count, c->mtu);
+		c->wq_desc_count, c->rq_desc_count,
+		enic->rte_dev->data->mtu, enic->max_mtu);
 	dev_info(enic_get_dev(enic), "vNIC csum tx/rx %s/%s "
 		"rss %s intr mode %s type %s timer %d usec "
 		"loopback tag 0x%04x\n",
diff --git a/drivers/net/enic/enic_res.h b/drivers/net/enic/enic_res.h
index 3c8e303..303530e 100644
--- a/drivers/net/enic/enic_res.h
+++ b/drivers/net/enic/enic_res.h
@@ -46,7 +46,9 @@ 
 #define ENIC_MAX_RQ_DESCS		4096
 
 #define ENIC_MIN_MTU			68
-#define ENIC_MAX_MTU			9000
+
+/* Does not include (possible) inserted VLAN tag and FCS */
+#define ENIC_DEFAULT_MAX_PKT_SIZE	9022
 
 #define ENIC_MULTICAST_PERFECT_FILTERS	32
 #define ENIC_UNICAST_PERFECT_FILTERS	32