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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0C309C19F2D for ; Sat, 6 Aug 2022 08:59:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241835AbiHFI7T (ORCPT ); Sat, 6 Aug 2022 04:59:19 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54632 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241790AbiHFI7J (ORCPT ); Sat, 6 Aug 2022 04:59:09 -0400 Received: from mail-ed1-x533.google.com (mail-ed1-x533.google.com [IPv6:2a00:1450:4864:20::533]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C56AB16593 for ; Sat, 6 Aug 2022 01:59:06 -0700 (PDT) Received: by mail-ed1-x533.google.com with SMTP id b16so5934538edd.4 for ; Sat, 06 Aug 2022 01:59:06 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=3871ruND0nqZUe2qICGzGQqrskPExm04SE4C1XZsJ8o=; b=ZY+zRK3kKzOlXDBqE7+YeZFTpnrXzUt3GkZXVTtB5iU6c8286dqfKaxJNbUKlkpB7Z CQsa+yAKydvH6CKwZTMwSEhN5a6jgyRq9L3qg3YvVekqOSNgAYkXkjSAQpOGL8tpI6FV RIJJL7N4P4OHVJQTtV9yD1hvEQ5qmbzq7kSpHDvpqDzSk0COfcKtVu+GKNG5mWoF59M6 fqSxVIzb+thLLBFMn9YuRV6mJ9pKpU4kYQGonoch1YtcllOtGiwOE0J/7HJc1ZW55GZK CbflHra272yreW0uICNNYLC0Ne7ynT9K19IeSB7IkNXEm6YasI7f+zW3GUpIwG7TbdLm ThSQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to; bh=3871ruND0nqZUe2qICGzGQqrskPExm04SE4C1XZsJ8o=; b=awTnZPasO7XxIPXbH78S8i4tdsCYDwsoJJZtT4/KliFUM+xlxyy/onVBX3Nuw9fhKt up+UfWeg1mU7axkZ1D4iu/UMFVducRJ94UZnbb8KDU52/oklfebHX5IKLAExJNOI8KUO JO+tUJ7igQ9sRl2BJ4OelWEJwsI4XQ1Deg4HMQ6KhIAiAqk66wDdgOrt3ZIV/Si0zxzq +c7f3viWJufdOf7xobVqoCcnl5HZsnJm5sbpM2V0Cnj8Y61kvZMeKKWijgrpOtegeCie P7X6KyxP1fKCgXRLqQIqwpfGlBZ4ERm0wdBzrN/s4OsU4UKG+MZIPpnryQ0rJbxUQ68s 3ccA== X-Gm-Message-State: ACgBeo3kZIhD/kyub5yPu/phYV30s5CFrHwt+KOV4uJS2yQStP/1yxYP vfL/6hMM33WOYJ4kp7kwKTo= X-Google-Smtp-Source: AA6agR6zzMXGg7/Rm6mSBvH9lCwN98uU6d62QJ7mGE2xoiMZPRaPzYmQtya3LzUp5RsTXnSUYPc0xA== X-Received: by 2002:a05:6402:2b8f:b0:43a:66d4:a025 with SMTP id fj15-20020a0564022b8f00b0043a66d4a025mr9990648edb.121.1659776345408; Sat, 06 Aug 2022 01:59:05 -0700 (PDT) Received: from gmail.com (195-38-112-141.pool.digikabel.hu. [195.38.112.141]) by smtp.gmail.com with ESMTPSA id u1-20020a1709061da100b0072f5fa11d19sm2412559ejh.202.2022.08.06.01.59.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 06 Aug 2022 01:59:04 -0700 (PDT) Sender: Ingo Molnar Date: Sat, 6 Aug 2022 10:59:03 +0200 From: Ingo Molnar To: Rik van Riel Cc: Borislav Petkov , x86@kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com, Dave Hansen , Thomas Gleixner , Andy Lutomirski Subject: Re: [PATCH v3] x86,mm: print likely CPU at segfault time Message-ID: References: <20220805101644.2e674553@imladris.surriel.com> <20220805104007.115359b5@imladris.surriel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Ingo Molnar wrote: > > instrumentation_begin(); > > - handle_page_fault(regs, error_code, address); > > + handle_page_fault(regs, error_code, address, cpu); > > Not convinced that this is a good change: this will bloat all the > affected code by a couple of dozen instructions - for no good reason in > the context of this patch. > > Boris, why should we do this? Extracting a parameter at higher levels and > passing it down to lower levels is almost always a bad idea from a code > generation POV, unless the majority of lower levels needs this > information anyway (which isn't the case here). Oh, I just got to this series in my mbox: [RFC PATCH 0/5] Print CPU at segfault time ... [RFC PATCH 5/5] x86/entry: Store CPU info on exception entry With that basis, printing the segfault CPU becomes a 'free' feature. At the cost of putting ~2 new instructions into the hotpath of every exception though. :-/ Thanks, Ingo