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From:   Alexei Starovoitov <alexei.starovoitov@gmail.com>
Date:   Tue, 20 Jun 2023 08:32:33 -0700
Message-ID: <CAADnVQK_dWhPxdjs4HuAXWBTeVAf01er15dZU8tC+d=g6QCPXw@mail.gmail.com>
Subject: Re: [PATCH v2 06/12] mm/execmem: introduce execmem_data_alloc()
To:     Steven Rostedt <rostedt@goodmis.org>
Cc:     Thomas Gleixner <tglx@linutronix.de>,
        Kent Overstreet <kent.overstreet@linux.dev>,
        Mike Rapoport <rppt@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
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On Tue, Jun 20, 2023 at 7:51=E2=80=AFAM Steven Rostedt <rostedt@goodmis.org=
> wrote:
>
> On Mon, 19 Jun 2023 02:43:58 +0200
> Thomas Gleixner <tglx@linutronix.de> wrote:
>
> > Now you might argue that it _is_ a "hotpath" due to the BPF usage, but
> > then even more so as any intermediate wrapper which converts from one
> > data representation to another data representation is not going to
> > increase performance, right?
>
> Just as a side note. BPF can not attach its return calling code to
> functions that have more than 6 parameters (3 on 32 bit x86), because of
> the way BPF return path trampoline works. It is a requirement that all
> parameters live in registers, and none on the stack.

It's actually 7 and that restriction is being lifted.
The patch set to attach to <=3D 12 is being discussed.