From: Jakub Kicinski <kuba@kernel.org>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>,
ast@kernel.org, john.fastabend@gmail.com, netdev@vger.kernel.org,
bpf@vger.kernel.org
Subject: Re: [PATCH bpf-next 2/6] bpf, net: rework cookie generator as per-cpu one
Date: Fri, 25 Sep 2020 08:31:57 -0700 [thread overview]
Message-ID: <20200925083157.21df654d@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> (raw)
In-Reply-To: <c9fee768-4f35-e596-001b-2e2a0e4f48a1@gmail.com>
On Fri, 25 Sep 2020 17:15:17 +0200 Eric Dumazet wrote:
> On 9/25/20 5:00 PM, Jakub Kicinski wrote:
> > Is this_cpu_inc() in itself atomic?
To answer my own question - it is :)
> > unlikely((val & (COOKIE_LOCAL_BATCH - 1)) == 0))
> >
> > Can we reasonably assume we won't have more than 4k CPUs and just
> > statically divide this space by encoding CPU id in top bits?
>
> This might give some food to side channel attacks, since this would
> give an indication of cpu that allocated the id.
>
> Also, I hear that some distros enabled 8K cpus.
Ok :(
next prev parent reply other threads:[~2020-09-25 15:32 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-24 18:21 [PATCH bpf-next 0/6] Various BPF helper improvements Daniel Borkmann
2020-09-24 18:21 ` [PATCH bpf-next 1/6] bpf: add classid helper only based on skb->sk Daniel Borkmann
2020-09-25 14:46 ` Jakub Kicinski
2020-09-25 15:35 ` Daniel Borkmann
2020-09-24 18:21 ` [PATCH bpf-next 2/6] bpf, net: rework cookie generator as per-cpu one Daniel Borkmann
2020-09-24 18:58 ` Eric Dumazet
2020-09-24 22:03 ` Daniel Borkmann
2020-09-25 7:49 ` Eric Dumazet
2020-09-25 9:26 ` Daniel Borkmann
2020-09-25 15:00 ` Jakub Kicinski
2020-09-25 15:15 ` Eric Dumazet
2020-09-25 15:31 ` Jakub Kicinski [this message]
2020-09-25 15:45 ` Eric Dumazet
2020-09-24 18:21 ` [PATCH bpf-next 3/6] bpf: add redirect_neigh helper as redirect drop-in Daniel Borkmann
2020-09-24 22:12 ` David Ahern
2020-09-24 22:19 ` Daniel Borkmann
2020-09-24 18:21 ` [PATCH bpf-next 4/6] bpf, libbpf: add bpf_tail_call_static helper for bpf programs Daniel Borkmann
2020-09-24 20:53 ` Andrii Nakryiko
2020-09-24 22:17 ` Daniel Borkmann
2020-09-25 15:42 ` Daniel Borkmann
2020-09-25 15:52 ` Daniel Borkmann
2020-09-25 16:50 ` Andrii Nakryiko
2020-09-25 19:52 ` Daniel Borkmann
2020-09-25 6:13 ` Yonghong Song
2020-09-24 18:21 ` [PATCH bpf-next 5/6] bpf, selftests: use bpf_tail_call_static where appropriate Daniel Borkmann
2020-09-24 19:25 ` Maciej Fijalkowski
2020-09-24 22:03 ` Daniel Borkmann
2020-09-24 18:21 ` [PATCH bpf-next 6/6] bpf, selftests: add redirect_neigh selftest Daniel Borkmann
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=20200925083157.21df654d@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com \
--to=kuba@kernel.org \
--cc=ast@kernel.org \
--cc=bpf@vger.kernel.org \
--cc=daniel@iogearbox.net \
--cc=eric.dumazet@gmail.com \
--cc=john.fastabend@gmail.com \
--cc=netdev@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
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;
as well as URLs for NNTP newsgroup(s).