linux-kernel - Re: [PATCH 0/2] bpf: Yet another approach to fix the BPF dispatcher thing

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Message-ID: <875yfwrw7q.fsf@all.your.base.are.belong.to.us>
Date:   Thu, 03 Nov 2022 14:42:01 +0100
From:   Björn Töpel <bjorn@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>, olsajiri@...il.com,
        ast@...nel.org, daniel@...earbox.net
Cc:     linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        bpf@...r.kernel.org, peterz@...radead.org, toke@...hat.com,
        David.Laight@...lab.com, rostedt@...dmis.org
Subject: Re: [PATCH 0/2] bpf: Yet another approach to fix the BPF dispatcher
 thing

Peter Zijlstra <peterz@...radead.org> writes:

> Hi!
>
> Even thought the __attribute__((patchable_function_entry())) solution to the
> BPF dispatcher woes works, it turns out to not be supported by the whole range
> of ageing compilers we support. Specifically this attribute seems to be GCC-8
> and later.
>
> This is another approach -- using static_call() to rewrite the dispatcher
> function. I've compile tested this on:
>
>   x86_64  (inline static-call support)
>   i386    (out-of-line static-call support)
>   aargh64 (no static-call support)
>
> A previous version was tested and found working by Bjorn.
>
> It is split in two patches; first reverting the current approach and then
> introducing the new for ease of review.

Took it for a spin on x86_64/KVM. For the series:

Acked-by: Björn Töpel <bjorn@...nel.org>
Tested-by: Björn Töpel <bjorn@...nel.org>