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 B3C68C54E94 for ; Wed, 25 Jan 2023 17:50:26 +0000 (UTC) Received: from list by lists.xenproject.org with outflank-mailman.484506.751104 (Exim 4.92) (envelope-from ) id 1pKjuI-0006Y9-GM; Wed, 25 Jan 2023 17:49:58 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 484506.751104; Wed, 25 Jan 2023 17:49:58 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1pKjuI-0006Y2-By; Wed, 25 Jan 2023 17:49:58 +0000 Received: by outflank-mailman (input) for mailman id 484506; Wed, 25 Jan 2023 17:49:57 +0000 Received: from se1-gles-flk1-in.inumbo.com ([94.247.172.50] helo=se1-gles-flk1.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1pKjuH-0006Xw-Ml for xen-devel@lists.xenproject.org; Wed, 25 Jan 2023 17:49:57 +0000 Received: from ppsw-43.srv.uis.cam.ac.uk (ppsw-43.srv.uis.cam.ac.uk [131.111.8.143]) by se1-gles-flk1.inumbo.com (Halon) with ESMTPS id ac85d094-9cd8-11ed-b8d1-410ff93cb8f0; Wed, 25 Jan 2023 18:49:54 +0100 (CET) Received: from hades.srcf.societies.cam.ac.uk ([131.111.179.67]:39600) by ppsw-43.srv.uis.cam.ac.uk (ppsw.cam.ac.uk [131.111.8.139]:25) with esmtps (TLS1.2:ECDHE-RSA-AES256-GCM-SHA384:256) id 1pKjuD-000T2l-V4 (Exim 4.96) (return-path ); Wed, 25 Jan 2023 17:49:53 +0000 Received: from [10.80.2.8] (default-46-102-197-194.interdsl.co.uk [46.102.197.194]) (Authenticated sender: amc96) by hades.srcf.societies.cam.ac.uk (Postfix) with ESMTPSA id 713F61FA26; Wed, 25 Jan 2023 17:49:53 +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: ac85d094-9cd8-11ed-b8d1-410ff93cb8f0 X-Cam-AntiVirus: no malware found X-Cam-ScannerInfo: https://help.uis.cam.ac.uk/email-scanner-virus Message-ID: Date: Wed, 25 Jan 2023 17:49:53 +0000 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.7.1 Content-Language: en-GB To: Jan Beulich , "xen-devel@lists.xenproject.org" Cc: Andrew Cooper , Wei Liu , =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= References: <930254a6-d0c8-4910-982a-bfd227187240@suse.com> From: Andrew Cooper Subject: Re: [PATCH v3 0/4] x86/spec-ctrl: IPBP improvements In-Reply-To: <930254a6-d0c8-4910-982a-bfd227187240@suse.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 25/01/2023 3:24 pm, Jan Beulich wrote: > Versions of the two final patches were submitted standalone earlier > on. The series here tries to carry out a suggestion from Andrew, > which the two of us have been discussing. Then said previously posted > patches are re-based on top, utilizing the new functionality. > > 1: spec-ctrl: add logic to issue IBPB on exit to guest > 2: spec-ctrl: defer context-switch IBPB until guest entry > 3: limit issuing of IBPB during context switch > 4: PV: issue branch prediction barrier when switching 64-bit guest to kernel mode In the subject, you mean IBPB.  I think all the individual patches are fine. Do you have an implementation of VMASST_TYPE_mode_switch_no_ibpb for Linux yet?  The thing I'd like to avoid is that we commit this perf it to Xen, without lining Linux up to be able to skip it. ~Andrew