From: David Laight <David.Laight@ACULAB.COM>
To: 'Ard Biesheuvel' <ardb@kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Cc: "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
"bpf@vger.kernel.org" <bpf@vger.kernel.org>,
"arnd@arndb.de" <arnd@arndb.de>,
Nick Desaulniers <ndesaulniers@google.com>,
Arvind Sankar <nivedita@alum.mit.edu>,
"Randy Dunlap" <rdunlap@infradead.org>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Peter Zijlstra <peterz@infradead.org>,
Geert Uytterhoeven <geert@linux-m68k.org>,
"Kees Cook" <keescook@chromium.org>
Subject: RE: [PATCH] bpf: don't rely on GCC __attribute__((optimize)) to disable GCSE
Date: Thu, 29 Oct 2020 08:38:02 +0000 [thread overview]
Message-ID: <445378db7beb4d588b95709251eeb00b@AcuMS.aculab.com> (raw)
In-Reply-To: <20201027205723.12514-1-ardb@kernel.org>
From: Ard Biesheuvel
> Sent: 27 October 2020 20:57
>
> Commit 3193c0836f203 ("bpf: Disable GCC -fgcse optimization for
> ___bpf_prog_run()") introduced a __no_fgcse macro that expands to a
> function scope __attribute__((optimize("-fno-gcse"))), to disable a
> GCC specific optimization that was causing trouble on x86 builds, and
> was not expected to have any positive effect in the first place.
Surely it is possibly to 'adjust' the bpf code so that gcc doesn't
apply (and can't apply) the gcse optimisation?
David
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Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
prev parent reply other threads:[~2020-10-29 8:39 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-27 20:57 [PATCH] bpf: don't rely on GCC __attribute__((optimize)) to disable GCSE Ard Biesheuvel
2020-10-27 21:20 ` Nick Desaulniers
2020-10-27 21:49 ` Ard Biesheuvel
2020-10-27 22:03 ` Nick Desaulniers
2020-10-27 22:23 ` Ard Biesheuvel
2020-10-27 22:38 ` Nick Desaulniers
2020-10-27 23:04 ` Daniel Borkmann
2020-10-27 23:11 ` Nick Desaulniers
2020-10-28 8:11 ` [PATCH] tools/perf: Remove broken __no_tail_call attribute Peter Zijlstra
2020-10-28 8:14 ` Ard Biesheuvel
2020-10-28 12:24 ` Miguel Ojeda
2020-10-28 6:51 ` [PATCH] bpf: don't rely on GCC __attribute__((optimize)) to disable GCSE Ard Biesheuvel
2020-10-28 6:59 ` Ard Biesheuvel
2020-10-28 8:30 ` Geert Uytterhoeven
2020-10-29 8:38 ` David Laight [this message]
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