From: Yuri Benditovich <yuri.benditovich@daynix.com>
To: "David S. Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>,
"Michael S . Tsirkin" <mst@redhat.com>,
Jason Wang <jasowang@redhat.com>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
Yonghong Song <yhs@fb.com>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@kernel.org>,
rdunlap@infradead.org, willemb@google.com, gustavoars@kernel.org,
herbert@gondor.apana.org.au, steffen.klassert@secunet.com,
nogikh@google.com, pablo@netfilter.org, decui@microsoft.com,
cai@lca.pw, jakub@cloudflare.com, elver@google.com,
pabeni@redhat.com, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
virtualization@lists.linux-foundation.org, bpf@vger.kernel.org
Cc: Yan Vugenfirer <yan@daynix.com>
Subject: Re: [RFC PATCH 0/7] Support for virtio-net hash reporting
Date: Tue, 12 Jan 2021 21:49:21 +0200 [thread overview]
Message-ID: <CAOEp5OejaX4ZETThrj4-n8_yZoeTZs56CBPHbQqNsR2oni8dWw@mail.gmail.com> (raw)
In-Reply-To: <20210112194143.1494-1-yuri.benditovich@daynix.com>
On Tue, Jan 12, 2021 at 9:41 PM Yuri Benditovich
<yuri.benditovich@daynix.com> wrote:
>
> Existing TUN module is able to use provided "steering eBPF" to
> calculate per-packet hash and derive the destination queue to
> place the packet to. The eBPF uses mapped configuration data
> containing a key for hash calculation and indirection table
> with array of queues' indices.
>
> This series of patches adds support for virtio-net hash reporting
> feature as defined in virtio specification. It extends the TUN module
> and the "steering eBPF" as follows:
>
> Extended steering eBPF calculates the hash value and hash type, keeps
> hash value in the skb->hash and returns index of destination virtqueue
> and the type of the hash. TUN module keeps returned hash type in
> (currently unused) field of the skb.
> skb->__unused renamed to 'hash_report_type'.
>
> When TUN module is called later to allocate and fill the virtio-net
> header and push it to destination virtqueue it populates the hash
> and the hash type into virtio-net header.
>
> VHOST driver is made aware of respective virtio-net feature that
> extends the virtio-net header to report the hash value and hash report
> type.
Comment from Willem de Bruijn:
Skbuff fields are in short supply. I don't think we need to add one
just for this narrow path entirely internal to the tun device.
Instead, you could just run the flow_dissector in tun_put_user if the
feature is negotiated. Indeed, the flow dissector seems more apt to me
than BPF here. Note that the flow dissector internally can be
overridden by a BPF program if the admin so chooses.
This also hits on a deeper point with the choice of hash values, that
I also noticed in my RFC patchset to implement the inverse [1][2]. It
is much more detailed than skb->hash + skb->l4_hash currently offers,
and that can be gotten for free from most hardware. In most practical
cases, that information suffices. I added less specific fields
VIRTIO_NET_HASH_REPORT_L4, VIRTIO_NET_HASH_REPORT_OTHER that work
without explicit flow dissection. I understand that the existing
fields are part of the standard. Just curious, what is their purpose
beyond 4-tuple based flow hashing?
[1] https://patchwork.kernel.org/project/netdevbpf/list/?series=406859&state=*
[2] https://github.com/wdebruij/linux/commit/0f77febf22cd6ffc242a575807fa8382a26e511e
>
> Yuri Benditovich (7):
> skbuff: define field for hash report type
> vhost: support for hash report virtio-net feature
> tun: allow use of BPF_PROG_TYPE_SCHED_CLS program type
> tun: free bpf_program by bpf_prog_put instead of bpf_prog_destroy
> tun: add ioctl code TUNSETHASHPOPULATION
> tun: populate hash in virtio-net header when needed
> tun: report new tun feature IFF_HASH
>
> drivers/net/tun.c | 43 +++++++++++++++++++++++++++++++------
> drivers/vhost/net.c | 37 ++++++++++++++++++++++++-------
> include/linux/skbuff.h | 7 +++++-
> include/uapi/linux/if_tun.h | 2 ++
> 4 files changed, 74 insertions(+), 15 deletions(-)
>
> --
> 2.17.1
>
next prev parent reply other threads:[~2021-01-12 19:50 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-12 19:41 [RFC PATCH 0/7] Support for virtio-net hash reporting Yuri Benditovich
2021-01-12 19:41 ` [RFC PATCH 1/7] skbuff: define field for hash report type Yuri Benditovich
2021-01-12 19:41 ` [RFC PATCH 2/7] vhost: support for hash report virtio-net feature Yuri Benditovich
2021-01-12 19:41 ` [RFC PATCH 3/7] tun: allow use of BPF_PROG_TYPE_SCHED_CLS program type Yuri Benditovich
2021-01-12 19:46 ` Alexei Starovoitov
2021-01-12 20:33 ` Yuri Benditovich
2021-01-12 20:40 ` Yuri Benditovich
2021-01-12 20:55 ` Yuri Benditovich
2021-01-18 9:16 ` Yuri Benditovich
2021-01-20 18:44 ` Alexei Starovoitov
2021-01-24 11:52 ` Yuri Benditovich
2021-01-12 19:41 ` [RFC PATCH 4/7] tun: free bpf_program by bpf_prog_put instead of bpf_prog_destroy Yuri Benditovich
2021-01-12 19:41 ` [RFC PATCH 5/7] tun: add ioctl code TUNSETHASHPOPULATION Yuri Benditovich
2021-01-12 19:41 ` [RFC PATCH 6/7] tun: populate hash in virtio-net header when needed Yuri Benditovich
2021-01-12 19:41 ` [RFC PATCH 7/7] tun: report new tun feature IFF_HASH Yuri Benditovich
2021-01-12 19:49 ` Yuri Benditovich [this message]
2021-01-12 20:28 ` [RFC PATCH 0/7] Support for virtio-net hash reporting Yuri Benditovich
2021-01-12 23:47 ` Willem de Bruijn
2021-01-13 4:05 ` Jason Wang
2021-01-13 14:33 ` Willem de Bruijn
2021-01-14 3:38 ` Jason Wang
2021-01-17 7:57 ` Yuri Benditovich
2021-01-18 2:46 ` Jason Wang
2021-01-18 9:09 ` Yuri Benditovich
2021-01-18 15:19 ` Willem de Bruijn
-- strict thread matches above, loose matches on Subject: below --
2021-01-05 12:24 Yuri Benditovich
2021-01-05 17:21 ` Willem de Bruijn
2021-01-12 19:36 ` Yuri Benditovich
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