From: Peter Zijlstra <peterz@infradead.org>
To: Nick Desaulniers <ndesaulniers@google.com>
Cc: "Gustavo A. R. Silva" <gustavo@embeddedor.com>,
Joe Perches <joe@perches.com>,
Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>,
Ingo Molnar <mingo@redhat.com>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Jiri Olsa <jolsa@redhat.com>, Namhyung Kim <namhyung@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Borislav Petkov <bp@alien8.de>, "H. Peter Anvin" <hpa@zytor.com>,
"maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)"
<x86@kernel.org>, Kan Liang <kan.liang@linux.intel.com>,
linux-kernel <linux-kernel@vger.kernel.org>,
Kees Cook <keescook@chromium.org>, Shawn Landden <shawn@git.icu>,
Nathan Chancellor <natechancellor@gmail.com>,
Luc Van Oostenryck <luc.vanoostenryck@gmail.com>,
Chandler Carruth <chandlerc@google.com>
Subject: Re: [PATCH] perf/x86/intel: Mark expected switch fall-throughs
Date: Fri, 28 Jun 2019 15:31:05 +0200 [thread overview]
Message-ID: <20190628133105.GD3463@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20190627071250.GZ3402@hirez.programming.kicks-ass.net>
On Thu, Jun 27, 2019 at 09:12:50AM +0200, Peter Zijlstra wrote:
> Josh came up with the following:
>
> + /* If the jump target is close, do a 2-byte nop: */
> + ".skip -(%l[l_yes] - 1b <= 126), 0x66\n"
> + ".skip -(%l[l_yes] - 1b <= 126), 0x90\n"
> + /* Otherwise do a 5-byte nop: */
> + ".skip -(%l[l_yes] - 1b > 126), 0x0f\n"
> + ".skip -(%l[l_yes] - 1b > 126), 0x1f\n"
> + ".skip -(%l[l_yes] - 1b > 126), 0x44\n"
> + ".skip -(%l[l_yes] - 1b > 126), 0x00\n"
> + ".skip -(%l[l_yes] - 1b > 126), 0x00\n"
>
> Which is a wonderfully gruesome hack :-) So I'll be playing with that
> for a bit.
For those with interest; full patches at:
https://lkml.kernel.org/r/20190628102113.360432762@infradead.org
next prev parent reply other threads:[~2019-06-28 13:31 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-24 16:19 [PATCH] perf/x86/intel: Mark expected switch fall-throughs Gustavo A. R. Silva
2019-06-24 19:31 ` Peter Zijlstra
2019-06-24 19:45 ` Joe Perches
2019-06-24 20:37 ` Peter Zijlstra
2019-06-24 20:53 ` Gustavo A. R. Silva
2019-06-24 20:57 ` Joe Perches
2019-06-25 7:20 ` Peter Zijlstra
2019-06-24 22:28 ` Miguel Ojeda
2019-06-25 7:18 ` Peter Zijlstra
2019-06-25 12:47 ` Miguel Ojeda
2019-06-25 18:15 ` Nick Desaulniers
2019-06-25 22:29 ` Joe Perches
2019-06-25 22:57 ` Nick Desaulniers
2019-06-25 23:25 ` Joe Perches
2019-06-26 8:49 ` Peter Zijlstra
2019-06-26 22:14 ` Nick Desaulniers
2019-06-27 7:12 ` Peter Zijlstra
2019-06-28 13:31 ` Peter Zijlstra [this message]
2019-06-28 18:44 ` Nick Desaulniers
2019-06-29 7:10 ` Peter Zijlstra
2019-06-25 17:12 ` Kees Cook
2019-06-25 18:05 ` Nathan Chancellor
2019-06-25 19:53 ` Thomas Gleixner
2019-06-25 20:27 ` Nathan Chancellor
2019-06-25 20:37 ` Nick Desaulniers
2019-06-25 21:47 ` Thomas Gleixner
2019-06-26 5:10 ` Nathan Chancellor
2019-06-26 15:18 ` Thomas Gleixner
2019-06-26 19:00 ` Nathan Chancellor
2019-06-26 19:46 ` Thomas Gleixner
2019-06-26 20:03 ` Nathan Chancellor
2019-06-26 9:24 ` Peter Zijlstra
2019-06-26 9:55 ` Peter Zijlstra
2019-06-26 22:23 ` Nick Desaulniers
2019-06-27 7:35 ` Peter Zijlstra
2019-06-26 10:43 ` Peter Zijlstra
2019-06-26 22:15 ` Nick Desaulniers
2019-06-27 7:16 ` Peter Zijlstra
2019-06-26 16:30 ` Peter Zijlstra
2019-06-26 22:33 ` Nick Desaulniers
2019-06-26 23:11 ` Thomas Gleixner
2019-06-27 7:11 ` Peter Zijlstra
2019-06-25 23:46 ` Arnaldo Carvalho de Melo
2019-06-26 5:14 ` Nathan Chancellor
2019-06-25 20:09 ` Kees Cook
2019-06-26 8:06 ` Peter Zijlstra
2019-06-25 7:15 ` Peter Zijlstra
2019-07-25 16:27 ` [tip:perf/urgent] " tip-bot for Gustavo A. R. Silva
2019-07-25 17:06 ` Borislav Petkov
2019-07-25 17:35 ` Peter Zijlstra
2019-07-25 23:18 ` Joe Perches
2019-07-25 23:28 ` Kees Cook
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