Date:   Wed, 25 Jan 2023 10:13:26 -0600
From:   David Vernet <void@manifault.com>
To:     Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc:     bpf <bpf@vger.kernel.org>, Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Andrii Nakryiko <andrii@kernel.org>,
        Martin KaFai Lau <martin.lau@linux.dev>,
        Song Liu <song@kernel.org>, Yonghong Song <yhs@meta.com>,
        John Fastabend <john.fastabend@gmail.com>,
        KP Singh <kpsingh@kernel.org>,
        Stanislav Fomichev <sdf@google.com>,
        Hao Luo <haoluo@google.com>, Jiri Olsa <jolsa@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Kernel Team <kernel-team@meta.com>, Tejun Heo <tj@kernel.org>,
        Kumar Kartikeya Dwivedi <memxor@gmail.com>
Subject: Re: [PATCH bpf-next v3 2/7] bpf: Enable cpumasks to be queried and
 used as kptrs
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References: <20230125143816.721952-1-void@manifault.com>
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On Wed, Jan 25, 2023 at 08:01:49AM -0800, Alexei Starovoitov wrote:
> On Wed, Jan 25, 2023 at 6:38 AM David Vernet <void@manifault.com> wrote:
> > +
> > +void bpf_cpumask_set_cpu(u32 cpu, struct bpf_cpumask *cpumask)
> > +{
> > +       if (!cpu_valid(cpu))
> > +               return;
> > +
> > +       cpumask_set_cpu(cpu, (struct cpumask *)cpumask);
> 
> I was considering suggesting to use &cpumask->cpumask here and
> in other cases, but figured it's better to leave it as-is,
> since bpf prog will be doing this cast, so it matches.
> Maybe some build assertion is necessary to make sure it's the first member.
> Probably overkill as well.

IMO a build assertion is a good idea. Serves as documentation and a
sanity check. I'll send it out in a follow-on patch, unless you really
think it's overkill.

> 
> Applied.