From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.zytor.com (terminus.zytor.com [198.137.202.136]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E1071A29; Mon, 22 Jan 2024 02:16:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.137.202.136 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1705889769; cv=none; b=S7sCA+LtfrhoZcoe49QzxJv8L5RlSHq+0AGm17eHEUIgOmeLGnF0oA30lkVnEv1fP/FhuuSaDbvZWw8Y+TC8qHhpK49l+GIqQBodQfArEMJotB+fGlZ5vQ64NOG/qUtrM+UeM73JSZJSsQ1TGz6q6pm/5HCFtyGCA+Cm0WKUutY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1705889769; c=relaxed/simple; bh=NlE0A3R+sz1AENbMqNSyBeWJtkZ6eYpNoQcZqQZYgSU=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=C5heVrw3R+xkXzOsaf0JcxZoXdKUaMFDQe7DZQpGOI0HdWoZr35gLs7mYpYFh0VzuJNBOIHbEmeyX6PU6drmXGgQ0jY8psF75ZDaY0cZde0893I5V1dZYwowKzNL71GtTOgG9+QIW8AxBPdeUeDBSVEEjFmxFA9CSWwSO5ODEQs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zytor.com; spf=pass smtp.mailfrom=zytor.com; dkim=pass (2048-bit key) header.d=zytor.com header.i=@zytor.com header.b=kx2mpDiZ; arc=none smtp.client-ip=198.137.202.136 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zytor.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=zytor.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=zytor.com header.i=@zytor.com header.b="kx2mpDiZ" Received: from [IPV6:2601:646:8002:4640:ca4b:30a3:a7c4:4227] ([IPv6:2601:646:8002:4640:ca4b:30a3:a7c4:4227]) (authenticated bits=0) by mail.zytor.com (8.17.2/8.17.1) with ESMTPSA id 40M2FigV2293158 (version=TLSv1.3 cipher=TLS_AES_128_GCM_SHA256 bits=128 verify=NO); Sun, 21 Jan 2024 18:15:45 -0800 DKIM-Filter: OpenDKIM Filter v2.11.0 mail.zytor.com 40M2FigV2293158 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zytor.com; s=2024011201; t=1705889746; bh=jy1plg5e+XUmSLdqsgI3NMM7QyQk+y01Y5z5ug5i+Jk=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=kx2mpDiZXsFjyPz0GULGe/BaQJPLKkxNTSRtIPPY82/DQdULJFf6ya0n9SAURAWO/ 86Oafx2FFRtNst6LQAkpCuXgnqb+xafWz+vuDEq+VBRAaJn0dXoljd+39twuUTLSWh 3xrEmjc7pmrHf/81TCfRSZtl/hy89m2zsPuk7E5qSBKNPqgU24yYAIew8JH001vidf msA2LIKlYfU/sy3XB26sJh7awltViKYWCCsVSKcNkcQO849TPq9sNyxGnFKXx+ftrI LKGM+nyKGjPYVisH8dpAeiiYSrkM9O+smlGosVjnDo2/qIUCsvrL0Ke/p4vrGH3o+r YV7aU/cf1fCsA== Message-ID: <020a1803-25c4-4365-8c53-291becd94632@zytor.com> Date: Sun, 21 Jan 2024 18:15:39 -0800 Precedence: bulk X-Mailing-List: linux-toolchains@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/2] x86: Remove dynamic NOP selection To: Steven Rostedt Cc: Thorsten Glaser , Peter Zijlstra , x86@kernel.org, torvalds@linuxfoundation.org, linux-kernel@vger.kernel.org, linux-toolchains@vger.kernel.org, jpoimboe@redhat.com, alexei.starovoitov@gmail.com, mhiramat@kernel.org References: <20210312113253.305040674@infradead.org> <20210312115749.065275711@infradead.org> <20B57BDC-9A3F-4B02-9BA9-41477088A6CE@zytor.com> <20240121195649.7355e1d5@rorschach.local.home> Content-Language: en-US From: "H. Peter Anvin" In-Reply-To: <20240121195649.7355e1d5@rorschach.local.home> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 1/21/24 16:56, Steven Rostedt wrote: >> >> Yes, but it is a matter of where we optimize for performance as opposed to correctness. > > There is no such thing as "optimize for correctness", it is either > correct or it is not. Correctness should always come before performance > (at least that is what Thomas has pounded into me ;-) > > If a kernel use to work on a machine but a newer version no longer > works, I call that a regression. > There absolutely is such a thing as "optimize for correctness." It means to keep the code clean, easily testable, and with a minimal number of distinct code paths so that regressions and *especially* uncaught regressions get caught quickly. -hpa