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 22DE9C433B4 for ; Tue, 18 May 2021 10:20:48 +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 D4E6B611B0 for ; Tue, 18 May 2021 10:20:47 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D4E6B611B0 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=xen.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.129035.242217 (Exim 4.92) (envelope-from ) id 1liwq3-0006Zy-LH; Tue, 18 May 2021 10:20:35 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 129035.242217; Tue, 18 May 2021 10:20:35 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1liwq3-0006Zr-G4; Tue, 18 May 2021 10:20:35 +0000 Received: by outflank-mailman (input) for mailman id 129035; Tue, 18 May 2021 10:20:34 +0000 Received: from mail.xenproject.org ([104.130.215.37]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1liwq2-0006Zl-2G for xen-devel@lists.xenproject.org; Tue, 18 May 2021 10:20:34 +0000 Received: from xenbits.xenproject.org ([104.239.192.120]) by mail.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1liwq1-0000DD-RV; Tue, 18 May 2021 10:20:33 +0000 Received: from [54.239.6.187] (helo=a483e7b01a66.ant.amazon.com) by xenbits.xenproject.org with esmtpsa (TLS1.3:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.92) (envelope-from ) id 1liwq1-0000eh-Lg; Tue, 18 May 2021 10:20:33 +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=xen.org; s=20200302mail; h=Content-Transfer-Encoding:Content-Type:In-Reply-To: MIME-Version:Date:Message-ID:From:References:Cc:To:Subject; bh=JuAqfttAr0cqJXlEstfQXvr8kBJVIZtkS87RGGDsMy8=; b=EwpvBuvHE/lEv02EmNX1fo69Le 4PqJbOS1DGAAhLxVcK572WTcTeWKzPkOF8TZnY5B799kU2tmS82wsMqxpZpNzHdXw8UQVZT5MiQxl Qy+IJJKIPL09QsApTQqTgv6DFFkhvfH+CMvrG4kAWdCCALy74Tk94O3KgX/wCJwpzS0E=; Subject: Re: [PATCH 06/10] xen: replace order with nr_pfns in assign_pages for better compatibility To: Penny Zheng , xen-devel@lists.xenproject.org, sstabellini@kernel.org Cc: Bertrand.Marquis@arm.com, Wei.Chen@arm.com, nd@arm.com References: <20210518052113.725808-1-penny.zheng@arm.com> <20210518052113.725808-7-penny.zheng@arm.com> From: Julien Grall Message-ID: <7dc01bcd-1570-82fa-5d15-11c28a857b3f@xen.org> Date: Tue, 18 May 2021 11:20:31 +0100 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.10.1 MIME-Version: 1.0 In-Reply-To: <20210518052113.725808-7-penny.zheng@arm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 7bit Hi Penny, On 18/05/2021 06:21, Penny Zheng wrote: > Function parameter order in assign_pages is always used as 1ul << order, > referring to 2@order pages. > > Now, for better compatibility with new static memory, order shall > be replaced with nr_pfns pointing to page count with no constraint, > like 250MB. We have similar requirements for LiveUpdate because are preserving the memory with a number of pages (rather than a power-of-two). With the current interface would be need to split the range in a power of 2 which is a bit of pain. However, I think I would prefer if we introduce a new interface (maybe assign_pages_nr()) rather than change the meaning of the field. This is for two reasons: 1) We limit the risk to make mistake when backporting a patch touch assign_pages(). 2) Adding (1UL << order) for pretty much all the caller is not nice. Cheers, -- Julien Grall