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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7B5C2C6FD18 for ; Fri, 31 Mar 2023 12:54:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230488AbjCaMyS (ORCPT ); Fri, 31 Mar 2023 08:54:18 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59336 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230356AbjCaMyR (ORCPT ); Fri, 31 Mar 2023 08:54:17 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4A5CF199; Fri, 31 Mar 2023 05:54:15 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=Yeenr72+biii/gxq1Q+YDEgdmCOdBcLhSB08YsTUu+4=; b=cWuuNt3m2/7xaIpDp9GbqHfsJn /lptGcoV0wqRu41nyD9az7xdUuRHsgrDV9573SXFqElfIy1wjyd/TdCgBNU2rpuXQdRhNwzkJKyI1 vU7pmWIKyi0+cGgvee7Ay3pKnZPtHniMQu3SlqrCaKw/ozat3iNr5M+QcMJT/migWIoZ7z99Va0A+ LQ2gC/uT42y5Z8WLj2opMEIBevQMjZjNbiP49DfiZjoJBZ9ZFl3YVCtStLFCAui8J76Oi8k9FW68w DbwgUKhoGkZO0goGIlffRuckAhnykTFe0Zz5OKjPJ8QAx311Mr/l0Y/QMFwNBKXa7IF9Hxm5oudk3 vC7EWnJQ==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1piEGZ-00BQpk-1x; Fri, 31 Mar 2023 12:54:03 +0000 Date: Fri, 31 Mar 2023 13:54:03 +0100 From: Matthew Wilcox To: Kyungsan Kim Cc: lsf-pc@lists.linux-foundation.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-cxl@vger.kernel.org, a.manzanares@samsung.com, viacheslav.dubeyko@bytedance.com, dan.j.williams@intel.com, seungjun.ha@samsung.com, wj28.lee@samsung.com Subject: Re: Re: RE(2): FW: [LSF/MM/BPF TOPIC] SMDK inspired MM changes for CXL Message-ID: References: <20230331113715.400135-1-ks0204.kim@samsung.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230331113715.400135-1-ks0204.kim@samsung.com> Precedence: bulk List-ID: X-Mailing-List: linux-cxl@vger.kernel.org On Fri, Mar 31, 2023 at 08:37:15PM +0900, Kyungsan Kim wrote: > >> We resolved the issue using ZONE_EXMEM by allowing seletively choice of the two usecases. > > > >This sounds dangerously confused. Do you want the EXMEM to be removable > >or not? If you do, then allocations from it have to be movable. If > >you don't, why go to all this trouble? > > I'm sorry to make you confused. We will try more to clearly explain our thought. > We think the CXL DRAM device should be removable along with HW pluggable nature. > For MM point of view, we think a page of CXL DRAM can be both movable and unmovable. > An user or kernel context should be able to determine it. Thus, we think dedication on the ZONE_NORMAL or the ZONE_MOVABLE is not enough. No, this is not the right approach. If CXL is to be hot-pluggable, then all CXL allocations must be movable. If even one allocation on a device is not movable, then the device cannot be removed. ZONE_EXMEM feels like a solution in search of a problem.