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 lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 206C1C433EF for ; Wed, 1 Dec 2021 10:20:31 +0000 (UTC) Received: from list by lists.xenproject.org with outflank-mailman.235802.409002 (Exim 4.92) (envelope-from ) id 1msMif-000296-Vf; Wed, 01 Dec 2021 10:20:09 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 235802.409002; Wed, 01 Dec 2021 10:20:09 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1msMif-00028z-Sf; Wed, 01 Dec 2021 10:20:09 +0000 Received: by outflank-mailman (input) for mailman id 235802; Wed, 01 Dec 2021 10:20:09 +0000 Received: from se1-gles-sth1-in.inumbo.com ([159.253.27.254] helo=se1-gles-sth1.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1msMif-0001OS-04 for xen-devel@lists.xenproject.org; Wed, 01 Dec 2021 10:20:09 +0000 Received: from ppsw-33.csi.cam.ac.uk (ppsw-33.csi.cam.ac.uk [131.111.8.133]) by se1-gles-sth1.inumbo.com (Halon) with ESMTPS id 4170fbbd-5290-11ec-976b-d102b41d0961; Wed, 01 Dec 2021 11:20:07 +0100 (CET) Received: from hades.srcf.societies.cam.ac.uk ([131.111.179.67]:50558) by ppsw-33.csi.cam.ac.uk (ppsw.cam.ac.uk [131.111.8.137]:25) with esmtps (TLS1.2:ECDHE-RSA-AES256-GCM-SHA384:256) id 1msMic-000QlC-hn (Exim 4.95) (return-path ); Wed, 01 Dec 2021 10:20:06 +0000 Received: from [192.168.1.10] (host-92-12-61-86.as13285.net [92.12.61.86]) (Authenticated sender: amc96) by hades.srcf.societies.cam.ac.uk (Postfix) with ESMTPSA id 6BF2A1FC17; Wed, 1 Dec 2021 10:20:06 +0000 (GMT) X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: 4170fbbd-5290-11ec-976b-d102b41d0961 X-Cam-AntiVirus: no malware found X-Cam-ScannerInfo: https://help.uis.cam.ac.uk/email-scanner-virus Message-ID: Date: Wed, 1 Dec 2021 10:20:06 +0000 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.3.2 Subject: Re: [PATCH 1/4] x86/altcall: Check and optimise altcall targets Content-Language: en-GB To: Jan Beulich , Andrew Cooper Cc: =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= , Wei Liu , Xen-devel References: <20211126212258.7550-1-andrew.cooper3@citrix.com> <20211126212258.7550-2-andrew.cooper3@citrix.com> From: Andrew Cooper In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 01/12/2021 08:10, Jan Beulich wrote: > On 26.11.2021 22:22, Andrew Cooper wrote: >> @@ -279,6 +280,27 @@ static void init_or_livepatch _apply_alternatives(struct alt_instr *start, >> >> if ( dest ) >> { >> + /* >> + * When building for CET-IBT, all function pointer targets >> + * should have an endbr64 instruction. >> + * >> + * If this is not the case, leave a warning because >> + * something is wrong with the build. >> + * >> + * Otherwise, skip the endbr64 instruction. This is a >> + * marginal perf improvement which saves on instruction >> + * decode bandwidth. >> + */ >> + if ( IS_ENABLED(CONFIG_HAS_CC_CET_IBT) ) >> + { >> + if ( is_endbr64(dest) ) > I would have given my R-b, but I don't see where is_endbr64() is coming > from, and you don't list any prereqs here or in the cover letter. I'm > afraid I don't fancy going hunt for it in the many other pending patches. > Hence only on the assumption that the helper has got introduced before: > Reviewed-by: Jan Beulich Oh sorry - this series is based on the CET-IBT series, which adds CONFIG_HAS_CC_CET_IBT and is_endbr64(). ~Andrew