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=-5.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 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 6FB64C433E8 for ; Wed, 22 Jul 2020 23:49:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4765222B43 for ; Wed, 22 Jul 2020 23:49:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1595461759; bh=1IS+O/7YryqIBEkm5nkaKs05nC51c/pf8nsRFWQ6LdE=; h=Date:From:To:cc:Subject:In-Reply-To:References:List-ID:From; b=Vu82OVHcsRBXCkCeveiVP0b3ldcXUGbE7e+z70hwoZcLob2/Jg48fhion/wiYq12I mlrzkYUI4JKmHEmcaNou1RyjGBvrLcBubwHMky9m+FUujiHInwAui15JaniHu0iGux eBYQzA3B2crY6bE+pR/n4XDvKxjVq/0l6Y6nH4+c= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1733147AbgGVXtS (ORCPT ); Wed, 22 Jul 2020 19:49:18 -0400 Received: from mail.kernel.org ([198.145.29.99]:50194 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728607AbgGVXtS (ORCPT ); Wed, 22 Jul 2020 19:49:18 -0400 Received: from localhost (c-67-164-102-47.hsd1.ca.comcast.net [67.164.102.47]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 99E9320825; Wed, 22 Jul 2020 23:49:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1595461757; bh=1IS+O/7YryqIBEkm5nkaKs05nC51c/pf8nsRFWQ6LdE=; h=Date:From:To:cc:Subject:In-Reply-To:References:From; b=FrgmIjvmA70VVMfZFUF0EKllD6JAd0T3wuzJkEXkBHd9mk68R94zOTAVb1VshR80o VoedozueZTQ79QnhYsBQuIWbKhzLCmG3xMwCZYv104TVVJWpntgJlkPZ9kXSd1yIxs xBrz8+QmXgyh1brARc/h9Lq6CDqDU8ZD0/QxaBss= Date: Wed, 22 Jul 2020 16:49:16 -0700 (PDT) From: Stefano Stabellini X-X-Sender: sstabellini@sstabellini-ThinkPad-T480s To: Anchal Agarwal cc: Stefano Stabellini , Boris Ostrovsky , tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, x86@kernel.org, jgross@suse.com, linux-pm@vger.kernel.org, linux-mm@kvack.org, kamatam@amazon.com, konrad.wilk@oracle.com, roger.pau@citrix.com, axboe@kernel.dk, davem@davemloft.net, rjw@rjwysocki.net, len.brown@intel.com, pavel@ucw.cz, peterz@infradead.org, eduval@amazon.com, sblbir@amazon.com, xen-devel@lists.xenproject.org, vkuznets@redhat.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, dwmw@amazon.co.uk, benh@kernel.crashing.org Subject: Re: [PATCH v2 01/11] xen/manage: keep track of the on-going suspend mode In-Reply-To: <20200722180229.GA32316@dev-dsk-anchalag-2a-9c2d1d96.us-west-2.amazon.com> Message-ID: References: <20200702182136.GA3511@dev-dsk-anchalag-2a-9c2d1d96.us-west-2.amazon.com> <50298859-0d0e-6eb0-029b-30df2a4ecd63@oracle.com> <20200715204943.GB17938@dev-dsk-anchalag-2a-9c2d1d96.us-west-2.amazon.com> <0ca3c501-e69a-d2c9-a24c-f83afd4bdb8c@oracle.com> <20200717191009.GA3387@dev-dsk-anchalag-2a-9c2d1d96.us-west-2.amazon.com> <5464f384-d4b4-73f0-d39e-60ba9800d804@oracle.com> <20200721000348.GA19610@dev-dsk-anchalag-2a-9c2d1d96.us-west-2.amazon.com> <408d3ce9-2510-2950-d28d-fdfe8ee41a54@oracle.com> <20200722180229.GA32316@dev-dsk-anchalag-2a-9c2d1d96.us-west-2.amazon.com> User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="8323329-1520963972-1595461757=:17562" Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org This message is in MIME format. The first part should be readable text, while the remaining parts are likely unreadable without MIME-aware tools. --8323329-1520963972-1595461757=:17562 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT On Wed, 22 Jul 2020, Anchal Agarwal wrote: > On Tue, Jul 21, 2020 at 05:18:34PM -0700, Stefano Stabellini wrote: > > On Tue, 21 Jul 2020, Boris Ostrovsky wrote: > > > >>>>>> +static int xen_setup_pm_notifier(void) > > > >>>>>> +{ > > > >>>>>> + if (!xen_hvm_domain()) > > > >>>>>> + return -ENODEV; > > > >>>>>> > > > >>>>>> I forgot --- what did we decide about non-x86 (i.e. ARM)? > > > >>>>> It would be great to support that however, its out of > > > >>>>> scope for this patch set. > > > >>>>> I’ll be happy to discuss it separately. > > > >>>> > > > >>>> I wasn't implying that this *should* work on ARM but rather whether this > > > >>>> will break ARM somehow (because xen_hvm_domain() is true there). > > > >>>> > > > >>>> > > > >>> Ok makes sense. TBH, I haven't tested this part of code on ARM and the series > > > >>> was only support x86 guests hibernation. > > > >>> Moreover, this notifier is there to distinguish between 2 PM > > > >>> events PM SUSPEND and PM hibernation. Now since we only care about PM > > > >>> HIBERNATION I may just remove this code and rely on "SHUTDOWN_SUSPEND" state. > > > >>> However, I may have to fix other patches in the series where this check may > > > >>> appear and cater it only for x86 right? > > > >> > > > >> > > > >> I don't know what would happen if ARM guest tries to handle hibernation > > > >> callbacks. The only ones that you are introducing are in block and net > > > >> fronts and that's arch-independent. > > > >> > > > >> > > > >> You do add a bunch of x86-specific code though (syscore ops), would > > > >> something similar be needed for ARM? > > > >> > > > >> > > > > I don't expect this to work out of the box on ARM. To start with something > > > > similar will be needed for ARM too. > > > > We may still want to keep the driver code as-is. > > > > > > > > I understand the concern here wrt ARM, however, currently the support is only > > > > proposed for x86 guests here and similar work could be carried out for ARM. > > > > Also, if regular hibernation works correctly on arm, then all is needed is to > > > > fix Xen side of things. > > > > > > > > I am not sure what could be done to achieve any assurances on arm side as far as > > > > this series is concerned. > > > > Just to clarify: new features don't need to work on ARM or cause any > > addition efforts to you to make them work on ARM. The patch series only > > needs not to break existing code paths (on ARM and any other platforms). > > It should also not make it overly difficult to implement the ARM side of > > things (if there is one) at some point in the future. > > > > FYI drivers/xen/manage.c is compiled and working on ARM today, however > > Xen suspend/resume is not supported. I don't know for sure if > > guest-initiated hibernation works because I have not tested it. > > > > > > > > > If you are not sure what the effects are (or sure that it won't work) on > > > ARM then I'd add IS_ENABLED(CONFIG_X86) check, i.e. > > > > > > > > > if (!IS_ENABLED(CONFIG_X86) || !xen_hvm_domain()) > > > return -ENODEV; > > > > That is a good principle to have and thanks for suggesting it. However, > > in this specific case there is nothing in this patch that doesn't work > > on ARM. From an ARM perspective I think we should enable it and > > &xen_pm_notifier_block should be registered. > > > This question is for Boris, I think you we decided to get rid of the notifier > in V3 as all we need to check is SHUTDOWN_SUSPEND state which sounds plausible > to me. So this check may go away. It may still be needed for sycore_ops > callbacks registration. > > Given that all guests are HVM guests on ARM, it should work fine as is. > > > > > > I gave a quick look at the rest of the series and everything looks fine > > to me from an ARM perspective. I cannot imaging that the new freeze, > > thaw, and restore callbacks for net and block are going to cause any > > trouble on ARM. The two main x86-specific functions are > > xen_syscore_suspend/resume and they look trivial to implement on ARM (in > > the sense that they are likely going to look exactly the same.) > > > Yes but for now since things are not tested I will put this > !IS_ENABLED(CONFIG_X86) on syscore_ops calls registration part just to be safe > and not break anything. > > > > One question for Anchal: what's going to happen if you trigger a > > hibernation, you have the new callbacks, but you are missing > > xen_syscore_suspend/resume? > > > > Is it any worse than not having the new freeze, thaw and restore > > callbacks at all and try to do a hibernation? > If callbacks are not there, I don't expect hibernation to work correctly. > These callbacks takes care of xen primitives like shared_info_page, > grant table, sched clock, runstate time which are important to save the correct > state of the guest and bring it back up. Other patches in the series, adds all > the logic to these syscore callbacks. Freeze/thaw/restore are just there for at driver > level. I meant the other way around :-) Let me rephrase the question. Do you think that implementing freeze/thaw/restore at the driver level without having xen_syscore_suspend/resume can potentially make things worse compared to not having freeze/thaw/restore at the driver level at all? --8323329-1520963972-1595461757=:17562--