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

[Thomas Monjalon <thomas@monjalon.net>]

This proposal had no conclusion.
The examples have been fixed:
	http://dpdk.org/commit/5e470a6654

But there is still an inconsistency in the API:
"
 - for normal frames: zero max_rx_pkt_len uses a default
 - for jumbo frames: zero max_rx_pkt_len gives an error
"


01/08/2017 00:33, Thomas Monjalon:
> 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:
> > >> 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.
> > 
> > 
> > > This ethdev patch is about a behaviour change of the API.
> > 
> > The behaviour was not documented, so IMO it is not an issue.
> > 
> > 
> > > It is about considering 0 as a request for default value
> > > and return an error if a value cannot be set.
> > 
> > Right.
> > 
> > 
> > > 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
> > 
> 
> 
> 
>