From: "Toke Høiland-Jørgensen" <toke@redhat•com>
To: "Niklas Söderlund" <niklas.soderlund@corigine•com>
Cc: Lorenzo Bianconi <lorenzo@kernel•org>,
bpf@vger•kernel.org, netdev@vger•kernel.org, ast@kernel•org,
daniel@iogearbox•net, andrii@kernel•org, davem@davemloft•net,
kuba@kernel•org, hawk@kernel•org, pabeni@redhat•com,
edumazet@google•com, memxor@gmail•com, alardam@gmail•com,
saeedm@nvidia•com, anthony.l.nguyen@intel•com,
gospo@broadcom•com, vladimir.oltean@nxp•com, nbd@nbd•name,
john@phrozen•org, leon@kernel•org, simon.horman@corigine•com,
aelior@marvell•com, christophe.jaillet@wanadoo•fr,
ecree.xilinx@gmail•com, mst@redhat•com, bjorn@kernel•org,
magnus.karlsson@intel•com, maciej.fijalkowski@intel•com,
intel-wired-lan@lists•osuosl.org, lorenzo.bianconi@redhat•com
Subject: Re: [RFC v2 bpf-next 2/7] drivers: net: turn on XDP features
Date: Tue, 17 Jan 2023 23:42:07 +0100 [thread overview]
Message-ID: <87pmbcbx6o.fsf@toke.dk> (raw)
In-Reply-To: <Y8chM32w/ZWsOOT+@oden.dyn.berto.se>
Niklas Söderlund <niklas.soderlund@corigine•com> writes:
> On 2023-01-17 23:15:47 +0100, Toke Høiland-Jørgensen wrote:
>> Niklas Söderlund <niklas.soderlund@corigine•com> writes:
>>
>> > Hi Toke,
>> >
>> > On 2023-01-17 22:58:57 +0100, Toke Høiland-Jørgensen wrote:
>> >> Niklas Söderlund <niklas.soderlund@corigine•com> writes:
>> >>
>> >> > Hi Lorenzo and Marek,
>> >> >
>> >> > Thanks for your work.
>> >> >
>> >> > On 2023-01-14 16:54:32 +0100, Lorenzo Bianconi wrote:
>> >> >
>> >> > [...]
>> >> >
>> >> >>
>> >> >> Turn 'hw-offload' feature flag on for:
>> >> >> - netronome (nfp)
>> >> >> - netdevsim.
>> >> >
>> >> > Is there a definition of the 'hw-offload' written down somewhere? From
>> >> > reading this series I take it is the ability to offload a BPF program?
>> >>
>> >> Yeah, basically this means "allows loading and attaching programs in
>> >> XDP_MODE_HW", I suppose :)
>> >>
>> >> > It would also be interesting to read documentation for the other flags
>> >> > added in this series.
>> >>
>> >> Yup, we should definitely document them :)
>> >>
>> >> > [...]
>> >> >
>> >> >> diff --git a/drivers/net/ethernet/netronome/nfp/nfp_net_common.c
>> >> >> b/drivers/net/ethernet/netronome/nfp/nfp_net_common.c
>> >> >> index 18fc9971f1c8..5a8ddeaff74d 100644
>> >> >> --- a/drivers/net/ethernet/netronome/nfp/nfp_net_common.c
>> >> >> +++ b/drivers/net/ethernet/netronome/nfp/nfp_net_common.c
>> >> >> @@ -2529,10 +2529,14 @@ static void nfp_net_netdev_init(struct nfp_net *nn)
>> >> >> netdev->features &= ~NETIF_F_HW_VLAN_STAG_RX;
>> >> >> nn->dp.ctrl &= ~NFP_NET_CFG_CTRL_RXQINQ;
>> >> >>
>> >> >> + nn->dp.netdev->xdp_features = NETDEV_XDP_ACT_BASIC |
>> >> >> + NETDEV_XDP_ACT_HW_OFFLOAD;
>> >> >
>> >> > If my assumption about the 'hw-offload' flag above is correct I think
>> >> > NETDEV_XDP_ACT_HW_OFFLOAD should be conditioned on that the BPF firmware
>> >> > flavor is in use.
>> >> >
>> >> > nn->dp.netdev->xdp_features = NETDEV_XDP_ACT_BASIC;
>> >> >
>> >> > if (nn->app->type->id == NFP_APP_BPF_NIC)
>> >> > nn->dp.netdev->xdp_features |= NETDEV_XDP_ACT_HW_OFFLOAD;
>> >> >
>> >> >> +
>> >> >> /* Finalise the netdev setup */
>> >> >> switch (nn->dp.ops->version) {
>> >> >> case NFP_NFD_VER_NFD3:
>> >> >> netdev->netdev_ops = &nfp_nfd3_netdev_ops;
>> >> >> + nn->dp.netdev->xdp_features |= NETDEV_XDP_ACT_XSK_ZEROCOPY;
>> >> >> break;
>> >> >> case NFP_NFD_VER_NFDK:
>> >> >> netdev->netdev_ops = &nfp_nfdk_netdev_ops;
>> >> >
>> >> > This is also a wrinkle I would like to understand. Currently NFP support
>> >> > zero-copy on NFD3, but not for offloaded BPF programs. But with the BPF
>> >> > firmware flavor running the device can still support zero-copy for
>> >> > non-offloaded programs.
>> >> >
>> >> > Is it a problem that the driver advertises support for both
>> >> > hardware-offload _and_ zero-copy at the same time, even if they can't be
>> >> > used together but separately?
>> >>
>> >> Hmm, so the idea with this is to only expose feature flags that are
>> >> supported "right now" (you'll note that some of the drivers turn the
>> >> REDIRECT_TARGET flag on and off at runtime). Having features that are
>> >> "supported but in a different configuration" is one of the points of
>> >> user confusion we want to clear up with the explicit flags.
>> >>
>> >> So I guess it depends a little bit what you mean by "can't be used
>> >> together"? I believe it's possible to load two programs at the same
>> >> time, one in HW mode and one in native (driver) mode, right? In this
>> >> case, could the driver mode program use XSK zerocopy while the HW mode
>> >> program is also loaded?
>> >
>> > Exactly, this is my concern. Two programs can be loaded at the same
>> > time, one in HW mode and one in native mode. The program in native mode
>> > can use zero-copy at the same time as another program runs in HW mode.
>> >
>> > But the program running in HW mode can never use zero-copy.
>>
>> Hmm, but zero-copy is an AF_XDP feature, and AFAIK offloaded programs
>> can't use AF_XDP at all? So the zero-copy "feature" is available on the
>> hardware, it's just intrinsic to that feature that it doesn't work on
>> offloaded programs?
>
> That is true, so this is indeed not an issue then. Thanks for the
> clarification.
Cool - you're welcome :)
-Toke
next prev parent reply other threads:[~2023-01-17 23:10 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-14 15:54 [RFC v2 bpf-next 0/7] xdp: introduce xdp-feature support Lorenzo Bianconi
2023-01-14 15:54 ` [RFC v2 bpf-next 1/7] netdev-genl: create a simple family for netdev stuff Lorenzo Bianconi
2023-01-14 15:54 ` [RFC v2 bpf-next 2/7] drivers: net: turn on XDP features Lorenzo Bianconi
2023-01-17 21:29 ` Niklas Söderlund
2023-01-17 21:58 ` Toke Høiland-Jørgensen
2023-01-17 22:05 ` Niklas Söderlund
2023-01-17 22:15 ` Toke Høiland-Jørgensen
2023-01-17 22:29 ` Niklas Söderlund
2023-01-17 22:42 ` Toke Høiland-Jørgensen [this message]
2023-01-17 23:45 ` Lorenzo Bianconi
2023-01-18 8:50 ` Niklas Söderlund
2023-01-18 9:38 ` Lorenzo Bianconi
2023-01-18 20:30 ` sdf
2023-01-19 14:23 ` Lorenzo Bianconi
2023-01-14 15:54 ` [RFC v2 bpf-next 3/7] xsk: add usage of XDP features flags Lorenzo Bianconi
2023-01-17 22:07 ` Yonghong Song
2023-01-17 23:34 ` Lorenzo Bianconi
2023-01-17 23:37 ` Yonghong Song
2023-01-14 15:54 ` [RFC v2 bpf-next 4/7] libbpf: add the capability to specify netlink proto in libbpf_netlink_send_recv Lorenzo Bianconi
2023-01-14 15:54 ` [RFC v2 bpf-next 5/7] libbpf: add API to get XDP/XSK supported features Lorenzo Bianconi
2023-01-18 0:58 ` Jakub Kicinski
2023-01-19 22:39 ` Lorenzo Bianconi
2023-01-14 15:54 ` [RFC v2 bpf-next 6/7] bpf: devmap: check XDP features in bpf_map_update_elem and __xdp_enqueue Lorenzo Bianconi
2023-01-14 15:54 ` [RFC v2 bpf-next 7/7] selftests/bpf: introduce XDP compliance test tool Lorenzo Bianconi
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=87pmbcbx6o.fsf@toke.dk \
--to=toke@redhat$(echo .)com \
--cc=aelior@marvell$(echo .)com \
--cc=alardam@gmail$(echo .)com \
--cc=andrii@kernel$(echo .)org \
--cc=anthony.l.nguyen@intel$(echo .)com \
--cc=ast@kernel$(echo .)org \
--cc=bjorn@kernel$(echo .)org \
--cc=bpf@vger$(echo .)kernel.org \
--cc=christophe.jaillet@wanadoo$(echo .)fr \
--cc=daniel@iogearbox$(echo .)net \
--cc=davem@davemloft$(echo .)net \
--cc=ecree.xilinx@gmail$(echo .)com \
--cc=edumazet@google$(echo .)com \
--cc=gospo@broadcom$(echo .)com \
--cc=hawk@kernel$(echo .)org \
--cc=intel-wired-lan@lists$(echo .)osuosl.org \
--cc=john@phrozen$(echo .)org \
--cc=kuba@kernel$(echo .)org \
--cc=leon@kernel$(echo .)org \
--cc=lorenzo.bianconi@redhat$(echo .)com \
--cc=lorenzo@kernel$(echo .)org \
--cc=maciej.fijalkowski@intel$(echo .)com \
--cc=magnus.karlsson@intel$(echo .)com \
--cc=memxor@gmail$(echo .)com \
--cc=mst@redhat$(echo .)com \
--cc=nbd@nbd$(echo .)name \
--cc=netdev@vger$(echo .)kernel.org \
--cc=niklas.soderlund@corigine$(echo .)com \
--cc=pabeni@redhat$(echo .)com \
--cc=saeedm@nvidia$(echo .)com \
--cc=simon.horman@corigine$(echo .)com \
--cc=vladimir.oltean@nxp$(echo .)com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox