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 385FF1714B7; Thu, 18 Sep 2025 14:35:15 +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=1758206119; cv=none; b=Z7zLfNy6h86+7t/HPRroj8sQWWeFpIUCfX7b6bVttP0h6hcdKgx4abjc0IH6NTz/Hx7e/O4+6sWHa94M+i0sSv9AJKC1lTqRBW6wnCdqs5k8wwi+ACTvBASF8AbbZ+drsuget3dChR0+71qAszRFSvjMnSykfwBFMbNRs/enia4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758206119; c=relaxed/simple; bh=VIfbwCXNDWDtTlUVZsn0jjASoSkdpxOCjZdzdj1LESQ=; h=Date:From:To:CC:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=L7FLBNAP4d3ztd0cEud+ZEjISj7+wXxBjiu8x1B3zX2+K+Y4AiwWRrKoyVI/fvEA23Abbfht+q1pfYhnt2YepqYEr/VW6KIVlF1Xlm22qumEBVPX+6PJN6+y427Bl+TrJZJTLWDHWI4Keltzg+U+I+WghASRNQ9obfIeSM+Jrpo= 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 4cSJ635XHDz6GDDt; Thu, 18 Sep 2025 22:33:31 +0800 (CST) Received: from frapeml500008.china.huawei.com (unknown [7.182.85.71]) by mail.maildlp.com (Postfix) with ESMTPS id AD5291400C8; Thu, 18 Sep 2025 22:35:07 +0800 (CST) Received: from localhost (10.47.69.66) by frapeml500008.china.huawei.com (7.182.85.71) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.1.2507.39; Thu, 18 Sep 2025 16:35:07 +0200 Date: Thu, 18 Sep 2025 15:35:03 +0100 From: Jonathan Cameron To: CC: , , , , , , , , , Alejandro Lucero Subject: Re: [PATCH v18 09/20] cxl: Define a driver interface for HPA free space enumeration Message-ID: <20250918153503.00004800@huawei.com> In-Reply-To: <20250918091746.2034285-10-alejandro.lucero-palau@amd.com> References: <20250918091746.2034285-1-alejandro.lucero-palau@amd.com> <20250918091746.2034285-10-alejandro.lucero-palau@amd.com> X-Mailer: Claws Mail 4.3.0 (GTK 3.24.42; x86_64-w64-mingw32) Precedence: bulk X-Mailing-List: linux-cxl@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 frapeml500008.china.huawei.com (7.182.85.71) 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. > + * @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. > + 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. > + if (!root) { > + dev_dbg(&endpoint->dev, "endpoint can not be related to a root port\n"); > + return ERR_PTR(-ENXIO); > + } > + > + root_port = &root->port; > + scoped_guard(rwsem_read, &cxl_rwsem.region) > + device_for_each_child(&root_port->dev, &ctx, find_max_hpa); > + > + if (!ctx.cxlrd) > + return ERR_PTR(-ENOMEM); > + > + *max_avail_contig = ctx.max_hpa; > + return ctx.cxlrd; > +} > +EXPORT_SYMBOL_NS_GPL(cxl_get_hpa_freespace, "CXL"); > + > +/* > + * TODO: those references released here should avoid the decoder to be > + * unregistered. That is an ominous sounding TODO for a v18. Perhaps add more on why this is still here. > + */ > +void cxl_put_root_decoder(struct cxl_root_decoder *cxlrd) > +{ > + put_device(cxlrd_dev(cxlrd)); > +} > +EXPORT_SYMBOL_NS_GPL(cxl_put_root_decoder, "CXL");