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 6B43643152; Fri, 13 Sep 2024 17:59:11 +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=1726250353; cv=none; b=PoCaF4kPdpslK96jgI/9loenfeOyST1A5QLBnzdCb6xrawn6QLNKeTCPNCtk7eIK3G5cZr5cvjAvgebfWffZOzBOvM0zndhDDQa3VxJapRM6SFkUVPPnEz35tjXsysp9AE8lDc2F5QJEhtZfAV1qN24vumPwdoux2AVB0pjcj8Y= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1726250353; c=relaxed/simple; bh=xbkEPkRtCJxtsa+lQcTqVFU/kYGUnrt9dhe3iUEjUZE=; h=Date:From:To:CC:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=r/GrTBHKeRe0A4vz6ncxp/vi/66dVDPVJ04DrHO4S/4XerNf0Xdk6gAyFT739fI90iGe0SHykos6M7QzWuBfrIwr2gACYwfB+LXercGrzIwLSOtOqTdwV3QOXHkx5XZV7HqXehs9mLV5iBsQP3Gj7bUOaoiN3i4WkwXWS+lW264= 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 [172.18.186.31]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4X525r53sxz6L6tJ; Sat, 14 Sep 2024 01:55:28 +0800 (CST) Received: from frapeml500008.china.huawei.com (unknown [7.182.85.71]) by mail.maildlp.com (Postfix) with ESMTPS id 150961400CA; Sat, 14 Sep 2024 01:59:09 +0800 (CST) Received: from localhost (10.48.150.243) 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; Fri, 13 Sep 2024 19:59:08 +0200 Date: Fri, 13 Sep 2024 18:59:06 +0100 From: Jonathan Cameron To: CC: , , , , , , , , , Alejandro Lucero Subject: Re: [PATCH v3 13/20] cxl: define a driver interface for DPA allocation Message-ID: <20240913185906.000008a2@Huawei.com> In-Reply-To: <20240907081836.5801-14-alejandro.lucero-palau@amd.com> References: <20240907081836.5801-1-alejandro.lucero-palau@amd.com> <20240907081836.5801-14-alejandro.lucero-palau@amd.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: 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: lhrpeml100006.china.huawei.com (7.191.160.224) To frapeml500008.china.huawei.com (7.182.85.71) On Sat, 7 Sep 2024 09:18:29 +0100 alejandro.lucero-palau@amd.com wrote: > From: Alejandro Lucero > > Region creation involves finding available DPA (device-physical-address) > capacity to map into HPA (host-physical-address) space. Given the HPA > capacity constraint, define an API, cxl_request_dpa(), that has the > flexibility to map the minimum amount of memory the driver needs to > operate vs the total possible that can be mapped given HPA availability. > > Factor out the core of cxl_dpa_alloc, that does free space scanning, > into a cxl_dpa_freespace() helper, and use that to balance the capacity > available to map vs the @min and @max arguments to cxl_request_dpa. > > Based on https://lore.kernel.org/linux-cxl/168592158743.1948938.7622563891193802610.stgit@dwillia2-xfh.jf.intel.com/ > > Signed-off-by: Alejandro Lucero > Co-developed-by: Dan Williams Trivial comment below. > + > +/** > + * cxl_request_dpa - search and reserve DPA given input constraints > + * @endpoint: an endpoint port with available decoders > + * @is_ram: DPA operation mode (ram vs pmem) > + * @min: the minimum amount of capacity the call needs > + * @max: extra capacity to allocate after min is satisfied > + * > + * Given that a region needs to allocate from limited HPA capacity it > + * may be the case that a device has more mappable DPA capacity than > + * available HPA. So, the expectation is that @min is a driver known > + * value for how much capacity is needed, and @max is based the limit of > + * how much HPA space is available for a new region. > + * > + * Returns a pinned cxl_decoder with at least @min bytes of capacity > + * reserved, or an error pointer. The caller is also expected to own the > + * lifetime of the memdev registration associated with the endpoint to > + * pin the decoder registered as well. > + */ > +struct cxl_endpoint_decoder *cxl_request_dpa(struct cxl_port *endpoint, > + bool is_ram, > + resource_size_t min, > + resource_size_t max) > +{ > + struct cxl_endpoint_decoder *cxled; > + enum cxl_decoder_mode mode; > + struct device *cxled_dev; > + resource_size_t alloc; > + int rc; > + > + if (!IS_ALIGNED(min | max, SZ_256M)) > + return ERR_PTR(-EINVAL); > + > + down_read(&cxl_dpa_rwsem); > + > + cxled_dev = device_find_child(&endpoint->dev, NULL, find_free_decoder); > + if (!cxled_dev) > + cxled = ERR_PTR(-ENXIO); > + else > + cxled = to_cxl_endpoint_decoder(cxled_dev); Does this need to be under the rwsem? If not cleaner to just check cxled_dev outside the lock and return the error directly. Also, in theory this could return NULL - in practice not but checking it for IS_ERR() is perhaps going to lead to a bug in the distant future. > + > + up_read(&cxl_dpa_rwsem); > + > + if (IS_ERR(cxled)) > + return cxled; > + > + if (is_ram) > + mode = CXL_DECODER_RAM; > + else > + mode = CXL_DECODER_PMEM; > + > + rc = cxl_dpa_set_mode(cxled, mode); > + if (rc) > + goto err; > + > + down_read(&cxl_dpa_rwsem); > + alloc = cxl_dpa_freespace(cxled, NULL, NULL); > + up_read(&cxl_dpa_rwsem); > + > + if (max) > + alloc = min(max, alloc); > + if (alloc < min) { > + rc = -ENOMEM; > + goto err; > + } > + > + rc = cxl_dpa_alloc(cxled, alloc); > + if (rc) > + goto err; > + > + return cxled; > +err: > + put_device(cxled_dev); > + return ERR_PTR(rc); > +} > +EXPORT_SYMBOL_NS_GPL(cxl_request_dpa, CXL);