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 6D8BE2032D; Tue, 30 Sep 2025 14:47:23 +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=1759243646; cv=none; b=KS+Fewb6Ditpk5qlKpb78KAlm4yfpsOj6k+XQLAtpb9fP9UfhEY7qM6Pfd3aC7WqKYEnyCs0jasSecpINLqYYUx5qb5j2Tf8t4swp6u8LZq/JX2VcGuiwmhZbrJ0IBePLz2c6/PIvrwybhjQjH32RAN4a4FKo0VKYvNOJobcu30= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759243646; c=relaxed/simple; bh=wBn3HeWAMo8n4FTUS1A7CqoJBnLIN4H3P06LOhms7Zg=; h=Date:From:To:CC:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=Afxx+RbwueTla+BCb3tj3KoO4WPfmn76iz5lrfpquIvnuZVfwDtYs0vZm0ffdcqADP0mVfsoxw/yp4RbariSrdtQfRu5nvGGPP/fvVLIU56F+bS5wqcbudf3Lew2w+5oukFtkbB0mdOjm8QnXciT0Rdv4BWz+PMUC7khMDC7GcI= 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 [172.18.186.231]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4cbgmv0x63z6M4mZ; Tue, 30 Sep 2025 22:44:15 +0800 (CST) Received: from dubpeml100005.china.huawei.com (unknown [7.214.146.113]) by mail.maildlp.com (Postfix) with ESMTPS id 1E4061402F5; Tue, 30 Sep 2025 22:47:22 +0800 (CST) Received: from localhost (10.203.177.15) by dubpeml100005.china.huawei.com (7.214.146.113) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Tue, 30 Sep 2025 15:47:21 +0100 Date: Tue, 30 Sep 2025 15:47:19 +0100 From: Jonathan Cameron To: Alejandro Lucero Palau CC: , , , , , , , , , Subject: Re: [PATCH v18 09/20] cxl: Define a driver interface for HPA free space enumeration Message-ID: <20250930154719.000000fd@huawei.com> In-Reply-To: <989dd1bf-adcd-4bd4-82fc-0497d615667a@amd.com> References: <20250918091746.2034285-1-alejandro.lucero-palau@amd.com> <20250918091746.2034285-10-alejandro.lucero-palau@amd.com> <20250918153503.00004800@huawei.com> <989dd1bf-adcd-4bd4-82fc-0497d615667a@amd.com> X-Mailer: Claws Mail 4.3.0 (GTK 3.24.42; x86_64-w64-mingw32) Precedence: bulk X-Mailing-List: netdev@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: lhrpeml500011.china.huawei.com (7.191.174.215) To dubpeml100005.china.huawei.com (7.214.146.113) On Wed, 24 Sep 2025 17:16:14 +0100 Alejandro Lucero Palau wrote: > On 9/18/25 15:35, Jonathan Cameron wrote: > > On Thu, 18 Sep 2025 10:17:35 +0100 > > wrote: > > > >> From: Alejandro Lucero > >> > >> CXL region creation involves allocating capacity from Device Physical Address > >> (DPA) and assigning it to decode a given Host Physical Address (HPA). Before > >> determining how much DPA to allocate the amount of available HPA must be > >> determined. Also, not all HPA is created equal, some HPA targets RAM, some > >> targets PMEM, some is prepared for device-memory flows like HDM-D and HDM-DB, > >> and some is HDM-H (host-only). > >> > >> In order to support Type2 CXL devices, wrap all of those concerns into > >> an API that retrieves a root decoder (platform CXL window) that fits the > >> specified constraints and the capacity available for a new region. > >> > >> Add a complementary function for releasing the reference to such root > >> decoder. > >> > >> Based on https://lore.kernel.org/linux-cxl/168592159290.1948938.13522227102445462976.stgit@dwillia2-xfh.jf.intel.com/ > >> > >> Signed-off-by: Alejandro Lucero > >> Reviewed-by: Jonathan Cameron > > Either I was half asleep or a few things have snuck in. > > > > See below. > > > >> + > >> +/** > >> + * cxl_get_hpa_freespace - find a root decoder with free capacity per constraints > >> + * @endpoint: the endpoint requiring the HPA > > The parameter seems to have changed. Make sure to point scripts/kernel-doc at each > > file to check for stuff like this. > > > OK. > > > > > >> + * @interleave_ways: number of entries in @host_bridges > >> + * @flags: CXL_DECODER_F flags for selecting RAM vs PMEM, and Type2 device > >> + * @max_avail_contig: output parameter of max contiguous bytes available in the > >> + * returned decoder > >> + * > >> + * Returns a pointer to a struct cxl_root_decoder > >> + * > >> + * The return tuple of a 'struct cxl_root_decoder' and 'bytes available given > >> + * in (@max_avail_contig))' is a point in time snapshot. If by the time the > >> + * caller goes to use this root decoder's capacity the capacity is reduced then > >> + * caller needs to loop and retry. > >> + * > >> + * The returned root decoder has an elevated reference count that needs to be > >> + * put with cxl_put_root_decoder(cxlrd). > >> + */ > >> +struct cxl_root_decoder *cxl_get_hpa_freespace(struct cxl_memdev *cxlmd, > >> + int interleave_ways, > >> + unsigned long flags, > >> + resource_size_t *max_avail_contig) > >> +{ > >> + struct cxl_root *root __free(put_cxl_root) = NULL; > > Nope to this. See the stuff in cleanup.h on why not. > > > I guess you mean to declare the pointer later on when assigned to the > object instead of a default NULL, as you point out later. yes. > > After reading the cleanup file, it is not clear to me if this is really > needed since there is no lock involved in that example for a potential bug. > Do it anyway. It's not about bugs today, but about fragile code patterns that may break later without it being obvious. > > >> + struct cxl_port *endpoint = cxlmd->endpoint; > >> + struct cxlrd_max_context ctx = { > >> + .host_bridges = &endpoint->host_bridge, > >> + .flags = flags, > >> + }; > >> + struct cxl_port *root_port; > >> + > >> + if (!endpoint) { > >> + dev_dbg(&cxlmd->dev, "endpoint not linked to memdev\n"); > >> + return ERR_PTR(-ENXIO); > >> + } > >> + > >> + root = find_cxl_root(endpoint); > > extra space, but should be > > struct cxl_root *root __free(put_cxl_root) = find_cxl_root(endpoint); > > anyway. > >