Re: [PATCH v3] ether: use a default for max Rx frame size in configure()

We are missing some comments about this proposal.

24/04/2017 16:50, Andriy Berestovskyy:

Hey Thomas,

On 21.04.2017 00:25, Thomas Monjalon wrote:

quoted

quoted

The hardware is different, there is not much we can do about it.

We can return an error if the max_rx_pkt_len cannot be set in the NIC.

Yes, we pass the value to the PMD, which might check the value and 
return an error.

 >> Nevertheless, we can fix the false comment and have a default for the
 >> jumbos, which is beneficial for the apps/examples.
 >
 > The examples are using a hardcoded value, so they need to be fixed
 > anyway.

We might change the hardcoded values to zeros once the patch is in. This 
will make the examples a bit more clear.

quoted

This ethdev patch is about a behaviour change of the API.

The behaviour was not documented, so IMO it is not an issue.

quoted

It is about considering 0 as a request for default value
and return an error if a value cannot be set.

Right.

quoted

It will require more agreements and changes in the drivers
for returning an error where appropriate.

IMO the changes are transparent for the PMDs (please see below), but it 
might affect some applications. Here is the change in API behaviour:

Before the patch:
jumbo == 0, max_rx_pkt_len == 0, RESULT: max_rx_pkt_len = ETHER_MAX_LEN
jumbo == 0, max_rx_pkt_len == 10, RESULT: max_rx_pkt_len = ETHER_MAX_LEN
jumbo == 0, max_rx_pkt_len == 1200, RESULT: max_rx_pkt_len = 1200
jumbo == 0, max_rx_pkt_len == 9K, RESULT: max_rx_pkt_len = ETHER_MAX_LEN

jumbo == 1, max_rx_pkt_len == 0, RESULT: ERROR
jumbo == 1, max_rx_pkt_len == 10, RESULT: ERROR
jumbo == 1, max_rx_pkt_len == 1200, RESULT: max_rx_pkt_len = 1200
jumbo == 1, max_rx_pkt_len == 9K, RESULT: ERROR or max_rx_pkt_len = 9K
jumbo == 1, max_rx_pkt_len == 90K, RESULT: ERROR


After the patch:
jumbo == 0, max_rx_pkt_len == 0, RESULT: max_rx_pkt_len = ETHER_MAX_LEN
jumbo == 0, max_rx_pkt_len == 10, RESULT: ERROR (changed)
jumbo == 0, max_rx_pkt_len == 1200, RESULT: max_rx_pkt_len = 1200
jumbo == 0, max_rx_pkt_len == 9K, RESULT: ERROR (changed)

jumbo == 1, max_rx_pkt_len == 0, RESULT: max_rx_pkt_len = dev_info()
jumbo == 1, max_rx_pkt_len == 10, RESULT: ERROR
jumbo == 1, max_rx_pkt_len == 1200, RESULT: max_rx_pkt_len = 1200
jumbo == 1, max_rx_pkt_len == 9K, RESULT: ERROR or max_rx_pkt_len = 9K
jumbo == 1, max_rx_pkt_len == 90K, RESULT: ERROR

Only the apps which requested too small or too big normal frames will be 
affected. In most cases it will be rather an error in the app...


Also I have looked through all the PMDs to confirm they are not 
affected. Here is the summary:

af_packet
configure() does not use max_rx_pkt_len
info() returns max_rx_pktlen = ETH_FRAME_LEN (1514)

ark
configure() does not use max_rx_pkt_len
info() returns max_rx_pktlen = ETH_FRAME_LEN (16K - 128)

avp
configure() does not use max_rx_pkt_len
info() returns max_rx_pktlen = avp->max_rx_pkt_len
rx_queue_setup() uses max_rx_pkt_len for scattering

bnx2x
configure() uses max_rx_pkt_len to set internal mtu
info() returns max_rx_pktlen = BNX2X_MAX_RX_PKT_LEN (15872)

bnxt
configure() uses max_rx_pkt_len to set internal mtu
info() returns max_rx_pktlen = BNXT_MAX_MTU + ETHER_HDR_LEN + 
ETHER_CRC_LEN + VLAN_TAG_SIZE (9000 + 14 + 4 + 4)

bonding
configure() does not use max_rx_pkt_len
info() returns max_rx_pktlen = internals->candidate_max_rx_pktlen or 
ETHER_MAX_JUMBO_FRAME_LEN (0x3F00)

cxgbe
configure() does not use max_rx_pkt_len
info() returns max_rx_pktlen = CXGBE_MAX_RX_PKTLEN (9000 + 14 + 4)
rx_queue_setup() checks max_rx_pkt_len boundaries

dpaa2
configure() does not use max_rx_pkt_len
info() returns max_rx_pktlen = DPAA2_MAX_RX_PKT_LEN (10240)

e1000 (em)
configure() does not use max_rx_pkt_len
info() returns max_rx_pktlen = em_get_max_pktlen() (0x2412, 0x1000, 
1518, 0x3f00, depends on model)

e1000 (igb)
configure() does not use max_rx_pkt_len
info() returns max_rx_pktlen = 0x3fff
start() writes max_rx_pkt_len to HW for jumbo frames only
start() uses max_rx_pkt_len for scattering

ena
configure() does not use max_rx_pkt_len
info() returns max_rx_pktlen = adapter->max_mtu
start() checks max_rx_pkt_len boundaries

enic
configure() does not use max_rx_pkt_len
info() returns max_rx_pktlen = enic->max_mtu + 14 + 4

fm10k
configure() does not use max_rx_pkt_len
info() returns max_rx_pktlen = FM10K_MAX_PKT_SIZE (15 * 1024)
start() uses max_rx_pkt_len for scattering

i40e
configure() does not use max_rx_pkt_len
info() returns max_rx_pktlen = I40E_FRAME_SIZE_MAX (9728)
rx_queue_config() checks max_rx_pkt_len boundaries

ixgbe
configure() does not use max_rx_pkt_len
info() returns max_rx_pktlen = 15872 (9728 for vf)
start() writes max_rx_pkt_len to HW for jumbo frames only
start() uses max_rx_pkt_len for scattering

kni
configure() does not use max_rx_pkt_len
info() returns max_rx_pktlen = UINT32_MAX

liquidio
configure() does not use max_rx_pkt_len
info() returns max_rx_pktlen = LIO_MAX_RX_PKTLEN (64K)
start() checks max_rx_pkt_len boundaries

mlx4
configure() uses max_rx_pkt_len for scattering
info() returns max_rx_pktlen = 65536

mlx5
configure() uses max_rx_pkt_len for scattering
info() returns max_rx_pktlen = 65536

nfp
configure() does not use max_rx_pkt_len
info() returns max_rx_pktlen = hw->mtu

null
configure() does not use max_rx_pkt_len
info() returns max_rx_pktlen = (uint32_t)-1

pcap
configure() does not use max_rx_pkt_len
info() returns max_rx_pktlen = (uint32_t)-1

qede
configure() uses max_rx_pkt_len for scattering + internal data
info() returns max_rx_pktlen = ETH_TX_MAX_NON_LSO_PKT_LEN (9700 - 4 - 4 
- 12 - 8)

ring
configure() does not use max_rx_pkt_len
info() returns max_rx_pktlen = (uint32_t)-1

sfc
configure() uses max_rx_pkt_len to set internal data
info() returns max_rx_pktlen = EFX_MAC_PDU_MAX (9202 + 14 + 4 + 4 + 16)

szedata2
configure() does not use max_rx_pkt_len
info() returns max_rx_pktlen = (uint32_t)-1

tap
configure() does not use max_rx_pkt_len
info() returns max_rx_pktlen = ETHER_MAX_VLAN_FRAME_LEN (1518 + 4)

thunderx
configure() uses max_rx_pkt_len for scattering + sets internal mtu
info() returns max_rx_pktlen = NIC_HW_MAX_FRS (9200)

vhost
configure() does not use max_rx_pkt_len
info() returns max_rx_pktlen = (uint32_t)-1

virtio
configure() does not use max_rx_pkt_len
info() returns max_rx_pktlen = VIRTIO_MAX_RX_PKTLEN (9728U)

vmxnet3
configure() does not use max_rx_pkt_len
info() returns max_rx_pktlen = 16384;

xenvirt
configure() does not use max_rx_pkt_len
info() returns max_rx_pktlen = 2048


Regards,
Andriy