From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from frasgout.his.huawei.com (frasgout.his.huawei.com [185.176.79.56]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A32241885AA; Fri, 23 Aug 2024 16:59:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=185.176.79.56 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724432385; cv=none; b=fUuluH6Wl+Q2bdKLkZ3ATiRDMDYW0s5vQXE4nenh8vxf4eNV8ZsWiiCg/MYMYW2VRNMfCBTSyw2q/4MmC1N0L4fMwfTS6HNB+7A8wnecq/7bIpWlt0RTN24+Tqx6b587j7K7qKMFSyBBp4EYQFJkh2pMGJLkh9rcoUWg3ik0Ubc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724432385; c=relaxed/simple; bh=e+hxT2QDndoJ143ERmmrHsR0wbLLWxCriqNkKR1iRdU=; h=Date:From:To:CC:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=tJ+BjeTYSG89Z2uFWvSvUTdZzOHqFXfgGFBnEwkSYLt5Hm21lhh70hujQmod0d6JLZeh0w38xwKcw074yltg69djWrRi8ihX+TFNO7ht6QD+m+3eGjfZgYqTvWOBsvPoX0hvE43zJhGtbdfJAtFp2w3jvPAJWxXA9PSnoAgug30= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=Huawei.com; spf=pass smtp.mailfrom=huawei.com; arc=none smtp.client-ip=185.176.79.56 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=Huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Received: from mail.maildlp.com (unknown [172.18.186.216]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4Wr5mp37sSz6J6Bp; Sat, 24 Aug 2024 00:55:54 +0800 (CST) Received: from lhrpeml500005.china.huawei.com (unknown [7.191.163.240]) by mail.maildlp.com (Postfix) with ESMTPS id 16902140A35; Sat, 24 Aug 2024 00:59:40 +0800 (CST) Received: from localhost (10.203.177.66) by lhrpeml500005.china.huawei.com (7.191.163.240) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.1.2507.39; Fri, 23 Aug 2024 17:59:39 +0100 Date: Fri, 23 Aug 2024 17:59:38 +0100 From: Jonathan Cameron To: CC: Dave Jiang , Fan Ni , "Navneet Singh" , Chris Mason , Josef Bacik , David Sterba , Petr Mladek , Steven Rostedt , Andy Shevchenko , Rasmus Villemoes , Sergey Senozhatsky , Jonathan Corbet , Andrew Morton , Dan Williams , Davidlohr Bueso , Alison Schofield , Vishal Verma , , , , , Subject: Re: [PATCH v3 13/25] cxl/region: Add sparse DAX region support Message-ID: <20240823175938.00000917@Huawei.com> In-Reply-To: <20240816-dcd-type2-upstream-v3-13-7c9b96cba6d7@intel.com> References: <20240816-dcd-type2-upstream-v3-0-7c9b96cba6d7@intel.com> <20240816-dcd-type2-upstream-v3-13-7c9b96cba6d7@intel.com> Organization: Huawei Technologies Research and Development (UK) Ltd. X-Mailer: Claws Mail 4.1.0 (GTK 3.24.33; x86_64-w64-mingw32) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-ClientProxiedBy: lhrpeml500005.china.huawei.com (7.191.163.240) To lhrpeml500005.china.huawei.com (7.191.163.240) On Fri, 16 Aug 2024 09:44:21 -0500 ira.weiny@intel.com wrote: > From: Navneet Singh > > Dynamic Capacity CXL regions must allow memory to be added or removed > dynamically. In addition to the quantity of memory available the > location of the memory within a DC partition is dynamic based on the > extents offered by a device. CXL DAX regions must accommodate the > sparseness of this memory in the management of DAX regions and devices. > > Introduce the concept of a sparse DAX region. Add a create_dc_region() > sysfs entry to create such regions. Special case DC capable regions to > create a 0 sized seed DAX device to maintain compatibility which > requires a default DAX device to hold a region reference. > > Indicate 0 byte available capacity until such time that capacity is > added. > > Sparse regions complicate the range mapping of dax devices. There is no > known use case for range mapping on sparse regions. Avoid the > complication by preventing range mapping of dax devices on sparse > regions. > > Interleaving is deferred for now. Add checks. > > Signed-off-by: Navneet Singh > Co-developed-by: Ira Weiny > Signed-off-by: Ira Weiny Reviewed-by: Jonathan Cameron