From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751149AbeDMUrE (ORCPT ); Fri, 13 Apr 2018 16:47:04 -0400 Received: from mx0a-00082601.pphosted.com ([67.231.145.42]:58374 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750783AbeDMUrC (ORCPT ); Fri, 13 Apr 2018 16:47:02 -0400 Subject: Re: [PATCH] x86/cpufeature: guard asm_volatile_goto usage with CC_HAVE_ASM_GOTO To: Peter Zijlstra References: <20180410204259.3981586-1-yhs@fb.com> <20180410210716.GI4082@hirez.programming.kicks-ass.net> <552d5866-912e-afde-f25a-77ae8390816d@fb.com> <20180413181924.GT4064@hirez.programming.kicks-ass.net> CC: Yonghong Song , , , , , , Thomas Gleixner , netdev , Jesper Dangaard Brouer From: Alexei Starovoitov Message-ID: Date: Fri, 13 Apr 2018 13:42:14 -0700 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.13; rv:45.0) Gecko/20100101 Thunderbird/45.8.0 MIME-Version: 1.0 In-Reply-To: <20180413181924.GT4064@hirez.programming.kicks-ass.net> Content-Type: text/plain; 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otherwise we might be encouraging > people to build the kernel proper without asm-goto. > I don't understand this concern. 1. arch/x86/Makefile does ifndef CC_HAVE_ASM_GOTO $(error Compiler lacks asm-goto support.) endif which is pretty strong statement of the kernel direction. 2. Even with this patch that adds #ifdef CC_HAVE_ASM_GOTO back the x86 arch still needs asm-goto in the compiler to be built. As far as I can see there are other places where asm-goto is open coded. So there is no 'encouraging'. Whereas if we do bpf specific marco we'd need to explain that to all bpf users and they would need to fix their user space scripts. Amount of user space breakage is unknown at this point.