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=-6.8 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,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 1774AC433E1 for ; Fri, 14 Aug 2020 13:35:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E76D12068E for ; Fri, 14 Aug 2020 13:35:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=citrix.com header.i=@citrix.com header.b="U1CiDBcZ" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728607AbgHNNfu (ORCPT ); Fri, 14 Aug 2020 09:35:50 -0400 Received: from esa1.hc3370-68.iphmx.com ([216.71.145.142]:37176 "EHLO esa1.hc3370-68.iphmx.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726196AbgHNNfr (ORCPT ); Fri, 14 Aug 2020 09:35:47 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=citrix.com; s=securemail; t=1597412147; h=date:from:to:cc:subject:message-id:references: mime-version:content-transfer-encoding:in-reply-to; bh=Vhg2qIv0Jz5uNB1to7SsFv5hNsQzCGoy7ntsgX816ME=; b=U1CiDBcZk1odElv4SojTnBSGXwXPhBkaRZVZk/CoBW0ullto4znGBiGG uHsf5+yOe5TM4xt5+ykkaT0K0rYGhjo3bcvLQEVoSoqYxXBQbhyMw67JN 3OBQzvUv8Tw+ohvEHxpm16tWiFRt7DnCHf2UeY5y3FeugHwP8L1o9Z+VU Y=; Authentication-Results: esa1.hc3370-68.iphmx.com; dkim=none (message not signed) header.i=none IronPort-SDR: 3kOFJD7N60ERtsB74qGJI3XB6PL0hrH37iAm0pbM5PNV/FQ6T6jmbeXASasblAXIeXQLqwqf0n B/Da4GKHV9G6vOYMwD44IXUGCJ3cYZz2PgjkPj0Fu8FehPYFdfIA/yqX5Wl/Wi5AdwnNtqOBNq 40Ye7b7xVui+0ZvJub15TmF7cyPT3T+Bh7pUD91DG/xaiMgJ/3oxy9ZFN8COrkdaJsAjZEg4WX mmGqnJVZd3jJ/pY7wNa7/8pzAw/ZVX0QKpqU1zHC70psBGvrmWKbneBDww7mnmZg+X4dW6syS7 mIA= X-SBRS: 2.7 X-MesageID: 24880445 X-Ironport-Server: esa1.hc3370-68.iphmx.com X-Remote-IP: 162.221.158.21 X-Policy: $RELAYED X-IronPort-AV: E=Sophos;i="5.76,312,1592884800"; d="scan'208";a="24880445" Date: Fri, 14 Aug 2020 15:35:36 +0200 From: Roger Pau =?utf-8?B?TW9ubsOp?= To: =?utf-8?B?SsO8cmdlbiBHcm/Dnw==?= CC: Christoph Hellwig , , Oleksandr Andrushchenko , David Airlie , Daniel Vetter , Boris Ostrovsky , Stefano Stabellini , Dan Carpenter , Wei Liu , "Yan Yankovskyi" , , , , David Hildenbrand , Michal Hocko , Dan Williams Subject: Re: [PATCH v4 2/2] xen: add helpers to allocate unpopulated memory Message-ID: <20200814133536.GL975@Air-de-Roger> References: <20200811094447.31208-1-roger.pau@citrix.com> <20200811094447.31208-3-roger.pau@citrix.com> <20200813073337.GA16160@infradead.org> <20200813075420.GC975@Air-de-Roger> <20200814072920.GA6126@infradead.org> <20200814095629.GJ975@Air-de-Roger> <20200814124724.GK975@Air-de-Roger> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-ClientProxiedBy: AMSPEX02CAS02.citrite.net (10.69.22.113) To AMSPEX02CL02.citrite.net (10.69.22.126) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Aug 14, 2020 at 02:54:38PM +0200, Jürgen Groß wrote: > On 14.08.20 14:47, Roger Pau Monné wrote: > > On Fri, Aug 14, 2020 at 12:27:32PM +0200, Jürgen Groß wrote: > > > On 14.08.20 11:56, Roger Pau Monné wrote: > > > > On Fri, Aug 14, 2020 at 08:29:20AM +0100, Christoph Hellwig wrote: > > > > > On Thu, Aug 13, 2020 at 09:54:20AM +0200, Roger Pau Monn?? wrote: > > > > > > On Thu, Aug 13, 2020 at 08:33:37AM +0100, Christoph Hellwig wrote: > > > > > > > On Tue, Aug 11, 2020 at 11:44:47AM +0200, Roger Pau Monne wrote: > > > > > > > > If enabled (because ZONE_DEVICE is supported) the usage of the new > > > > > > > > functionality untangles Xen balloon and RAM hotplug from the usage of > > > > > > > > unpopulated physical memory ranges to map foreign pages, which is the > > > > > > > > correct thing to do in order to avoid mappings of foreign pages depend > > > > > > > > on memory hotplug. > > > > > > > > > > > > > > So please just select ZONE_DEVICE if this is so much better rather > > > > > > > than maintaining two variants. > > > > > > > > > > > > We still need to other variant for Arm at least, so both need to be > > > > > > maintained anyway, even if we force ZONE_DEVICE on x86. > > > > > > > > > > Well, it still really helps reproducability if you stick to one > > > > > implementation of x86. > > > > > > > > > > The alternative would be an explicit config option to opt into it, > > > > > but just getting a different implementation based on a random > > > > > kernel option is strange. > > > > > > > > Would adding something like the chunk below to the patch be OK? > > > > > > > > ---8<--- > > > > diff --git a/drivers/xen/Kconfig b/drivers/xen/Kconfig > > > > index 018020b91baa..5f321a1319e6 100644 > > > > --- a/drivers/xen/Kconfig > > > > +++ b/drivers/xen/Kconfig > > > > @@ -328,7 +328,14 @@ config XEN_FRONT_PGDIR_SHBUF > > > > tristate > > > > config XEN_UNPOPULATED_ALLOC > > > > - bool > > > > - default y if ZONE_DEVICE && !ARM && !ARM64 > > > > + bool "Use unpopulated memory ranges for guest mappings" > > > > + depends on X86 > > > > + select ZONE_DEVICE > > > > + default y > > > > > > I'd rather use "default XEN_BACKEND" here, as mappings of other guest's > > > memory is rarely used for non-backend guests. > > > > There's also the privcmd and gnt devices which make heavy use of this, > > so I'm not sure only selecting by default on XEN_BACKEND is the best > > option. > > I just want to avoid that kernels built for running as Xen guest, but > not as dom0, will be forced to select ZONE_DEVICE. > > As privcmd is dom0-only, this is no problem. Oh, didn't know that, I somehow assumed privcmd would be available to all Xen guests regardless of whether dom0 support was selected. > In case you are worrying about gnt devices, I'd be fine to switch to > > default XEN_BACKEND || XEN_GNTDEV Sure. maybe even: default XEN_BACKEND || XEN_GNTDEV || XEN_DOM0 Do you want me to resend with this changed or are you happy to fixup if there are no further comments? Thanks, Roger.