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=-7.3 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,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 B98B7C43460 for ; Thu, 20 May 2021 09:27:37 +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 835E0613D8 for ; Thu, 20 May 2021 09:27:37 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 835E0613D8 Authentication-Results: mail.kernel.org; dmarc=fail (p=quarantine dis=none) header.from=suse.com 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.130818.244828 (Exim 4.92) (envelope-from ) id 1ljexg-0007AN-Pc; Thu, 20 May 2021 09:27:24 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 130818.244828; Thu, 20 May 2021 09:27:24 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1ljexg-0007AG-KN; Thu, 20 May 2021 09:27:24 +0000 Received: by outflank-mailman (input) for mailman id 130818; Thu, 20 May 2021 09:27:23 +0000 Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1ljexf-0007AA-3O for xen-devel@lists.xenproject.org; Thu, 20 May 2021 09:27:23 +0000 Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id 00e0c74f-3340-4325-be5a-8eafe6f91952; Thu, 20 May 2021 09:27:22 +0000 (UTC) Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 6CD17AE81; Thu, 20 May 2021 09:27:21 +0000 (UTC) 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: 00e0c74f-3340-4325-be5a-8eafe6f91952 X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1621502841; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=7rqhgH9R9B73ijK+Qc/m24+QJNhL73dhbh8I92A83hI=; b=ssiW7HuR6VuDhLIudyXNbhAV165+/yUOINVmdBJPkP8WqLcNoiN8AOtKJBbZ+nQfCHpM1U xKHfeJP9KHfu5WpHvPwYsuz3GgupGVwlyWbNCbesGicGw2X/S/Nd0tJ6dvBooobkjHXvdy AhZha3fFAbxoREIWUt7brmFhc9heTJQ= Subject: Re: [PATCH 03/10] xen/arm: introduce PGC_reserved To: Julien Grall , Penny Zheng Cc: Bertrand Marquis , Wei Chen , nd , "xen-devel@lists.xenproject.org" , "sstabellini@kernel.org" References: <20210518052113.725808-1-penny.zheng@arm.com> <20210518052113.725808-4-penny.zheng@arm.com> <2f4eb08e-261b-70c4-bcbc-e08db36a50a9@xen.org> <44b46f35-cc51-9274-77f2-cfd18c998a38@xen.org> From: Jan Beulich Message-ID: Date: Thu, 20 May 2021 11:27:20 +0200 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.10.2 MIME-Version: 1.0 In-Reply-To: <44b46f35-cc51-9274-77f2-cfd18c998a38@xen.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit On 20.05.2021 10:59, Julien Grall wrote: > On 20/05/2021 09:40, Penny Zheng wrote: >> Oh, Second thought on this. >> And I think you are referring to balloon in/out here, hmm, also, like > > Yes I am referring to balloon in/out. > >> I replied there: >> "For issues on ballooning out or in, it is not supported here. > > So long you are not using the solution in prod then you are fine (see > below)... But then we should make clear this feature is a tech preview. > >> Domain on Static Allocation and 1:1 direct-map are all based on >> dom0-less right now, so no PV, grant table, event channel, etc, considered. >> >> Right now, it only supports device got passthrough into the guest." > > So we are not creating the hypervisor node in the DT for dom0less domU. > However, the hypercalls are still accessible by a domU if it really > wants to use them. > > Therefore, a guest can easily mess up with your static configuration and > predictability. > > IMHO, this is a must to solve before "static memory" can be used in > production. I'm having trouble seeing why it can't be addressed right away: Such guests can balloon in only after they've ballooned out some pages, and such balloon-in requests would be satisfied from the same static memory that is associated by the guest anyway. Jan