> -----Original Message----- > From: Stephen Hemminger [mailto:stephen at networkplumber.org] > Sent: Monday, December 14, 2015 9:35 PM > To: Ananyev, Konstantin > Cc: Zhang, Helin; dev at dpdk.org; Tom Kiely > Subject: Re: [PATCH] ixgbe: Discard SRIOV transparent vlan packet headers. > > On Mon, 14 Dec 2015 19:57:10 +0000 > "Ananyev, Konstantin" <konstantin.ananyev at intel.com> wrote: > > > > > > > > -----Original Message----- > > > From: Stephen Hemminger [mailto:stephen at networkplumber.org] > > > Sent: Monday, December 14, 2015 7:25 PM > > > To: Ananyev, Konstantin > > > Cc: Zhang, Helin; dev at dpdk.org; Tom Kiely > > > Subject: Re: [PATCH] ixgbe: Discard SRIOV transparent vlan packet headers. > > > > > > On Mon, 14 Dec 2015 19:12:26 +0000 > > > "Ananyev, Konstantin" <konstantin.ananyev at intel.com> wrote: > > > > > > > > > > > > > > > > From: Stephen Hemminger [mailto:stephen at networkplumber.org] > > > > > Sent: Friday, December 11, 2015 4:59 PM > > > > > To: Zhang, Helin; Ananyev, Konstantin > > > > > Cc: dev at dpdk.org; Tom Kiely; Stephen Hemminger > > > > > Subject: [PATCH] ixgbe: Discard SRIOV transparent vlan packet headers. > > > > > > > > > > From: Tom Kiely <tkiely at brocade.com> > > > > > > > > > > SRIOV VFs support "transparent" vlans. Traffic from/to a VM > > > > > associated with a VF is tagged/untagged with the specified > > > > > vlan in a manner intended to be totally transparent to the VM. > > > > > > > > > > The vlan is specified by "ip link set <device> vf <n> vlan <v>". > > > > > The VM is not configured for any vlan on the VF and the VM > > > > > should never see these transparent vlan headers for that reason. > > > > > > > > > > However, in practice these vlan headers are being received by > > > > > the VM which discards the packets as that vlan is unknown to it. > > > > > The Linux kernel explicitly discards such vlan headers but DPDK > > > > > does not. > > > > > This patch mirrors the kernel behaviour for SRIOV VFs only > > > > > > > > > > > > I have few concerns about that approach: > > > > > > > > 1. I don't think vlan_tci info should *always* be stripped by vf RX > > > > routine. > > > > There could be configurations when that information might be needed by > > > > upper layer. > > > > Let say VF can be member of 2 or more VLANs and upper layer would like > > > > to have that information > > > > for further processing. > > > > Or special mirror VF, that does traffic snnoping, or something else. > > > > 2. Proposed implementation would introduce a slowdown for all VF RX > > > > routines. > > > > 3. From the description it seems like the aim is to clear VLAN > > > > information for the RX packet. > > > > Though the patch actually clears VLAN info only for the RX packet whose > > > > VLAN tag is not present inside SW copy of VFTA table. > > > > Which makes no much point to me: > > > > If VLAN is not present in HW VFTA table, then packet with that VLAN tag > > > > will be discarded by HW anyway. > > > > If it is present inside VFTA table (both SW & HW), then VLAN > > > > information would be preserved with and without the patch. > > > > > > > > If you need to clear VLAN information, why not to do it on the upper > > > > layer - inside your application itself? > > > > Either create some sort of wrapper around rx_burst(), or setup an RX > > > > call-back for your VF device. > > > > > > > > Konstantin > > > > > > > > > The aim is to get SRIOV to work when the transparent VLAN tag feature is > > > used. > > > Please talk to the Linux driver team. Similar code exists there in > > > ixgbevf_process_skb_fields. > > > > > > Ah ok, I realised what you are trying to achieve now: > > You setup HW VFTA[] from the PF, so from VF point of view SW copy of the > > VFTA[] remains unset. > > So HW will pass VLAN packet in, but then SW will clear VLAN tag. > > Ok, that clears #3 above, but I think #1,2 still remain. > > On the host, what configured is a vlan tag per VF per guest > > Tom had more info in the original mail. > > http://permalink.gmane.org/gmane.comp.networking.dpdk.devel/28932 > > > > > > > The other option is have a copy of all the receive logic which is only > > > used by VF code. > > > > Why that's the only option? > > Why can't you clear that VLAN information above the PMD layer? > > Keep/obtain a copy of VFTA[] somewhere on the upper layer, > > and do actual clear after rx_burst() returns? > > Konstantin > > The problem is that the guest is supposed to not see the VLAN tags (it has no > reason to), > but the hardware leaves a VLAN tag on there.
Yes, I understand what you are trying to achieve. What I am trying to say: 1. VLAN tag removing shouldn't be forced for all VFs. I think there are scenarios where existing behaviour (keeping vlan_tci and ol_flags intact) are what people need. One example would be mirror VF doing other VFs traffic snooping. Probably some other cases too. 2. The way you implemented it - it might cause a RX performance degradation (specially for VF). That's why I think it better to be implemented on top of PMD: i.e: some sort of wrapper that checks all packets returned by rx_burst() and clears vlan_tci if needed. That would give you desired behaviour and keep current implementation intact. Konstantin
