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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

  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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