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Message-ID: <CAADnVQK_dWhPxdjs4HuAXWBTeVAf01er15dZU8tC+d=g6QCPXw@mail.gmail.com>
Date: Tue, 20 Jun 2023 08:32:33 -0700
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: Thomas Gleixner <tglx@...utronix.de>,
Kent Overstreet <kent.overstreet@...ux.dev>,
Mike Rapoport <rppt@...nel.org>,
LKML <linux-kernel@...r.kernel.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Catalin Marinas <catalin.marinas@....com>,
Christophe Leroy <christophe.leroy@...roup.eu>,
"David S. Miller" <davem@...emloft.net>,
Dinh Nguyen <dinguyen@...nel.org>,
Heiko Carstens <hca@...ux.ibm.com>,
Helge Deller <deller@....de>,
Huacai Chen <chenhuacai@...nel.org>,
Luis Chamberlain <mcgrof@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Michael Ellerman <mpe@...erman.id.au>,
Nadav Amit <nadav.amit@...il.com>,
"Naveen N. Rao" <naveen.n.rao@...ux.ibm.com>,
Palmer Dabbelt <palmer@...belt.com>,
Puranjay Mohan <puranjay12@...il.com>,
Rick Edgecombe <rick.p.edgecombe@...el.com>,
Russell King <linux@...linux.org.uk>,
Song Liu <song@...nel.org>,
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Subject: Re: [PATCH v2 06/12] mm/execmem: introduce execmem_data_alloc()
On Tue, Jun 20, 2023 at 7:51 AM Steven Rostedt <rostedt@...dmis.org> wrote:
>
> On Mon, 19 Jun 2023 02:43:58 +0200
> Thomas Gleixner <tglx@...utronix.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 <= 12 is being discussed.
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