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, NICE_REPLY_A,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 C50A1C433DB for ; Thu, 4 Mar 2021 15:20:55 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id 7EBDC64FD3 for ; Thu, 4 Mar 2021 15:20:55 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7EBDC64FD3 Authentication-Results: mail.kernel.org; dmarc=pass (p=none dis=none) header.from=xenproject.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from list by lists.xenproject.org with outflank-mailman.93332.176191 (Exim 4.92) (envelope-from ) id 1lHpmJ-0004Sq-JQ; Thu, 04 Mar 2021 15:20:39 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 93332.176191; Thu, 04 Mar 2021 15:20:39 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lHpmJ-0004Sj-GH; Thu, 04 Mar 2021 15:20:39 +0000 Received: by outflank-mailman (input) for mailman id 93332; Thu, 04 Mar 2021 15:20:38 +0000 Received: from mail.xenproject.org ([104.130.215.37]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lHpmI-0004Se-43 for xen-devel@lists.xenproject.org; Thu, 04 Mar 2021 15:20:38 +0000 Received: from xenbits.xenproject.org ([104.239.192.120]) by mail.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lHpmH-0005gw-VO for xen-devel@lists.xenproject.org; Thu, 04 Mar 2021 15:20:37 +0000 Received: from iwj (helo=mariner.uk.xensource.com) by xenbits.xenproject.org with local-bsmtp (Exim 4.92) (envelope-from ) id 1lHpmH-0007ml-Se for xen-devel@lists.xenproject.org; Thu, 04 Mar 2021 15:20:37 +0000 Received: from iwj by mariner.uk.xensource.com with local (Exim 4.89) (envelope-from ) id 1lHpmE-0005cl-MT; Thu, 04 Mar 2021 15:20:34 +0000 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" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=xenproject.org; s=20200302mail; h=References:In-Reply-To:Subject:Cc:To:Date :Message-ID:Content-Transfer-Encoding:Content-Type:MIME-Version:From; bh=9x18qLadbxkQpIoQsoR+n91O/1aBxffFpXjJUt3fBMQ=; b=VGEH90BJDdM4enpv0Ljp/R5DuB 1aqUkmHJKrAIzOn+td44M51ukgWt49zWviisiY0UZvDUauuVckAC88roiQl05hDhBLiT1dP3iukkz FFpXjiJfWmBzux+V1VmGjjGS9KKUmBSyfJpHWJas2zzt+pfSVrqdI7i4HOjX+pMFpRow=; From: Ian Jackson MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8bit Message-ID: <24640.64194.445736.52546@mariner.uk.xensource.com> Date: Thu, 4 Mar 2021 15:20:34 +0000 To: Roger Pau =?iso-8859-1?Q?Monn=E9?= Cc: , Wei Liu , Anthony PERARD , Jan Beulich , Andrew Cooper , Jun Nakajima , Kevin Tian , Boris Ostrovsky Subject: Re: [PATCH v2 for-4.15] x86/msr: introduce an option for HVM relaxed rdmsr behavior In-Reply-To: References: <20210304144755.35891-1-roger.pau@citrix.com> <24640.62938.427877.757656@mariner.uk.xensource.com> X-Mailer: VM 8.2.0b under 24.5.1 (i686-pc-linux-gnu) Roger Pau Monné writes ("Re: [PATCH v2 for-4.15] x86/msr: introduce an option for HVM relaxed rdmsr behavior"): > On Thu, Mar 04, 2021 at 02:59:38PM +0000, Ian Jackson wrote: > > I think it's almost as bad to have guests which can be migrated in, > > but which then cannot reboot. > > Ups, yes, right. > > > Historically we have taken the view that new Xen must support old > > guests, even if that means being bug-compatible. So I am strongly in > > favour of avoiding such a usability regression. > > I'm not a xl/libxl expert, but couldn't we set the option in a > persistent way for migrated-in guests? > > IIRC at domain creation libxl knows whether it's a restore or a fresh > domain, and hence we could set the option there? > > The part I'm not sure is about how to make it persistent. The guest could be stopped with xl shutdown and then recrated with xl create, from the config file. I don't think we want to break that use case here either. Ian.