From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D4D67C4321A for ; Fri, 28 Jun 2019 13:31:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A7B94208E3 for ; Fri, 28 Jun 2019 13:31:29 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="DCJbIut9" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726798AbfF1Nb2 (ORCPT ); Fri, 28 Jun 2019 09:31:28 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:52946 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726566AbfF1Nb2 (ORCPT ); Fri, 28 Jun 2019 09:31:28 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=WWW87peQLpsz5hF+D7roPrdiHtXEaavrtIXlcnYMy1Q=; b=DCJbIut9E6YcoLpwlDbqM6bjg jSwlILW4EWr68yzvQf+B4qtTC60F/kkGKy2SDO0NEEISF/yza/RdM2RMq+WlWNvtH81TFWgqnJlQg rgXHKEXu/iTMzCqtpSYjDeMvBoYmGxyZ9JnVsljXbv0NA3dxPFFVq/1YNoOrHX0ZB2zYNGGkJmPUj Ccf4ofQoCJ5XaOh6pD41cQJEQipyZi1N1cg8KTCEtLl3sDyfCm7wpl/i36Mu+lQnge70hj/MFL3+k j363U9hbm0bmnZz2z/1JjYqOBtnCOrqcPwcibcrdj2zQiRYA5WcAYUSmC5B45nQcb4ZCbIn75PI/2 qahVgr6lw==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.92 #3 (Red Hat Linux)) id 1hgqy3-0005JE-Co; Fri, 28 Jun 2019 13:31:07 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 48F2E20AB898E; Fri, 28 Jun 2019 15:31:05 +0200 (CEST) Date: Fri, 28 Jun 2019 15:31:05 +0200 From: Peter Zijlstra To: Nick Desaulniers Cc: "Gustavo A. R. Silva" , Joe Perches , Miguel Ojeda , Ingo Molnar , Arnaldo Carvalho de Melo , Alexander Shishkin , Jiri Olsa , Namhyung Kim , Thomas Gleixner , Borislav Petkov , "H. Peter Anvin" , "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" , Kan Liang , linux-kernel , Kees Cook , Shawn Landden , Nathan Chancellor , Luc Van Oostenryck , Chandler Carruth Subject: Re: [PATCH] perf/x86/intel: Mark expected switch fall-throughs Message-ID: <20190628133105.GD3463@hirez.programming.kicks-ass.net> References: <20190624203737.GL3436@hirez.programming.kicks-ass.net> <3dc75cd4-9a8d-f454-b5fb-64c3e6d1f416@embeddedor.com> <20190625071846.GN3436@hirez.programming.kicks-ass.net> <20190626084927.GI3419@hirez.programming.kicks-ass.net> <20190627071250.GZ3402@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190627071250.GZ3402@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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