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=-8.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 D2FD7C433E1 for ; Fri, 14 Aug 2020 13:53:04 +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 A3C4B207DA for ; Fri, 14 Aug 2020 13:53:04 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A3C4B207DA Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1k6a8R-00083M-Oa; Fri, 14 Aug 2020 13:52:43 +0000 Received: from all-amaz-eas1.inumbo.com ([34.197.232.57] helo=us1-amaz-eas2.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1k6a8Q-00083H-Ce for xen-devel@lists.xenproject.org; Fri, 14 Aug 2020 13:52:42 +0000 X-Inumbo-ID: 75bdde3c-cb45-48c1-a132-5db3e7683907 Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-amaz-eas2.inumbo.com (Halon) with ESMTPS id 75bdde3c-cb45-48c1-a132-5db3e7683907; Fri, 14 Aug 2020 13:52:41 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 2F143B167; Fri, 14 Aug 2020 13:53:03 +0000 (UTC) Subject: Re: [PATCH v4 2/2] xen: add helpers to allocate unpopulated memory To: =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= Cc: Christoph Hellwig , linux-kernel@vger.kernel.org, Oleksandr Andrushchenko , David Airlie , Daniel Vetter , Boris Ostrovsky , Stefano Stabellini , Dan Carpenter , Wei Liu , Yan Yankovskyi , dri-devel@lists.freedesktop.org, xen-devel@lists.xenproject.org, linux-mm@kvack.org, David Hildenbrand , Michal Hocko , Dan Williams 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> <20200814133536.GL975@Air-de-Roger> From: =?UTF-8?B?SsO8cmdlbiBHcm/Dnw==?= Message-ID: <2f0e2484-d4ec-adb3-4182-6db2c542c633@suse.com> Date: Fri, 14 Aug 2020 15:52:39 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20200814133536.GL975@Air-de-Roger> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" On 14.08.20 15:35, Roger Pau Monné wrote: > 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. My remark above should have been more precise in this regard: privcmd operations dealing with foreign mappings are normally limited to dom0 (there might be special cases, like linux-based stubdoms, but those will be configured carefully for that purpose, so they don't need to be considered for selecting the default IMO). > >> 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 Yes. > > Do you want me to resend with this changed or are you happy to fixup > if there are no further comments? I'd prefer a resend (maybe after Patch 1 has gained its missing Ack, and then with Patch 1 sent to me, too). Juergen 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=-8.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 AECB8C433DF for ; Fri, 14 Aug 2020 14:03:45 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (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 6FF6120838 for ; Fri, 14 Aug 2020 14:03:45 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6FF6120838 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=dri-devel-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id C834A6EB5B; Fri, 14 Aug 2020 14:03:44 +0000 (UTC) Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by gabe.freedesktop.org (Postfix) with ESMTPS id B8B446EB5B for ; Fri, 14 Aug 2020 14:03:42 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 2F143B167; Fri, 14 Aug 2020 13:53:03 +0000 (UTC) Subject: Re: [PATCH v4 2/2] xen: add helpers to allocate unpopulated memory To: =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= 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> <20200814133536.GL975@Air-de-Roger> From: =?UTF-8?B?SsO8cmdlbiBHcm/Dnw==?= Message-ID: <2f0e2484-d4ec-adb3-4182-6db2c542c633@suse.com> Date: Fri, 14 Aug 2020 15:52:39 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20200814133536.GL975@Air-de-Roger> Content-Language: en-US X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Stefano Stabellini , Wei Liu , Oleksandr Andrushchenko , David Airlie , Yan Yankovskyi , David Hildenbrand , linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, Michal Hocko , Christoph Hellwig , linux-mm@kvack.org, xen-devel@lists.xenproject.org, Boris Ostrovsky , Dan Williams , Dan Carpenter Content-Transfer-Encoding: base64 Content-Type: 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