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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 A3927C433E6 for ; Thu, 11 Mar 2021 08:43:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 63CDA64FA8 for ; Thu, 11 Mar 2021 08:43:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231670AbhCKIm4 (ORCPT ); Thu, 11 Mar 2021 03:42:56 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41324 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231309AbhCKIml (ORCPT ); Thu, 11 Mar 2021 03:42:41 -0500 Received: from desiato.infradead.org (desiato.infradead.org [IPv6:2001:8b0:10b:1:d65d:64ff:fe57:4e05]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4976EC061574; Thu, 11 Mar 2021 00:42:41 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; 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; bh=iNur3LddLbqOxPZObj0ioFPvfinKVBSW9anyjtwfwJM=; b=WanEzgwFy9TFzNVXe3OsRG/IHe +z77vFr5wAdeiwyeKU9/63vQ/AtB1LaHCbqMYn3iPc97V5JHDGCASbLctR3UyHWhTnuwKn5na5HUR Z9dT+KOA47twNFbGCz71zvp8Cj6gGNJe2KKNKC6+zav92iIQuRujY2TNxTk2Syh2TYFau62sdkXb+ pk3BCo7z1N92aWL1Hl1qE1HtNE2PldWZYFdC6gLxu0LD15aklrkDWepqleY4zoMDzl32450+mUSfu mqdu2B6R4AeSq5zUGU0gUy7y2gkjJCizQ21sbnDHpLBYjlnPckdtNBUofSO09gALBBqkpgJGGIFqG KXKLP1xw==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.94 #2 (Red Hat Linux)) id 1lKGtU-008ghN-MZ; Thu, 11 Mar 2021 08:42:08 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id DF4D83010CF; Thu, 11 Mar 2021 09:42:05 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id D31EF299E3D08; Thu, 11 Mar 2021 09:42:05 +0100 (CET) Date: Thu, 11 Mar 2021 09:42:05 +0100 From: Peter Zijlstra To: Jarkko Sakkinen Cc: "Yu, Yu-cheng" , x86@kernel.org, "H. Peter Anvin" , Thomas Gleixner , Ingo Molnar , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-api@vger.kernel.org, Arnd Bergmann , Andy Lutomirski , Balbir Singh , Borislav Petkov , Cyrill Gorcunov , Dave Hansen , Eugene Syromiatnikov , Florian Weimer , "H.J. Lu" , Jann Horn , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , Randy Dunlap , "Ravi V. Shankar" , Vedvyas Shanbhogue , Dave Martin , Weijiang Yang , Pengfei Xu , Haitao Huang Subject: Re: [PATCH v22 8/8] x86/vdso: Add ENDBR64 to __vdso_sgx_enter_enclave Message-ID: References: <20210310220519.16811-1-yu-cheng.yu@intel.com> <20210310220519.16811-9-yu-cheng.yu@intel.com> <8b8efe44-b79f-ce29-ee28-066f88c93840@intel.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 On Thu, Mar 11, 2021 at 05:36:06AM +0200, Jarkko Sakkinen wrote: > Does it do any harm to put it there unconditionally? Blows up your text footprint and I$ pressure. These instructions are 4 bytes each. Aside from that, they're a NOP, so only consume front-end resources (hopefully) on older CPUs and when IBT is disabled.