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 0C76D2D5A0C; Tue, 7 Oct 2025 13:52:55 +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=1759845178; cv=none; b=DVIqKSfzgOi70vqs7NwxK4quuGoajTzv/feQg9zDLGl3HOc/vqGWUS/JT03OxeKk969aB00xljsgUsKFIsFYxSfteBmRxv0kQMKJq0J8LrI0pRcwttrb56laU1eHgsZrAWVkQ2Jcw/R63KxjLRT24usPAw3p1EOJfPGELSWc4p0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759845178; c=relaxed/simple; bh=HfxRrR8A9JYecxBT1fJHpunZBYqR4DP6Tso6Qv1Ifxg=; h=Date:From:To:CC:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=QZ0RT5n6l6or9uc4kYXe6LNQeg4LFiP+q4J+/jqwAD8QI/q9pjGmMQn32QwhoSAI25j0+U6p/FV4sdCqQ24FtRg9/B9A6FQW7Ng9MtNexuLt0RUHuMPqMpB4Fxs7Uk7W4xRA9GMcwyO8xXV439NDxdIoh9mOPrF+5pT1FhYaM/g= 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 4cgyDd01XRz6M4cb; Tue, 7 Oct 2025 21:49:37 +0800 (CST) Received: from dubpeml100005.china.huawei.com (unknown [7.214.146.113]) by mail.maildlp.com (Postfix) with ESMTPS id 335BD1400D9; Tue, 7 Oct 2025 21:52:54 +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, 7 Oct 2025 14:52:53 +0100 Date: Tue, 7 Oct 2025 14:52:51 +0100 From: Jonathan Cameron To: CC: , , , , , , , , , Alejandro Lucero Subject: Re: [PATCH v19 13/22] cxl: Define a driver interface for DPA allocation Message-ID: <20251007145251.0000526a@huawei.com> In-Reply-To: <20251006100130.2623388-14-alejandro.lucero-palau@amd.com> References: <20251006100130.2623388-1-alejandro.lucero-palau@amd.com> <20251006100130.2623388-14-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: lhrpeml100012.china.huawei.com (7.191.174.184) To dubpeml100005.china.huawei.com (7.214.146.113) On Mon, 6 Oct 2025 11:01:21 +0100 wrote: > From: Alejandro Lucero > > Region creation involves finding available DPA (device-physical-address) > capacity to map into HPA (host-physical-address) space. > > In order to support CXL Type2 devices, define an API, cxl_request_dpa(), > that tries to allocate the DPA memory the driver requires to operate.The > memory requested should not be bigger than the max available HPA obtained > previously with cxl_get_hpa_freespace(). > > Based on https://lore.kernel.org/linux-cxl/168592158743.1948938.7622563891193802610.stgit@dwillia2-xfh.jf.intel.com/ > > Signed-off-by: Alejandro Lucero A few minor things inline. Depending on how much this changed from the 'Based on' it might be appropriate to keep a SoB / author set to Dan, but I'll let him request that if he feels appropriate (or you can make that decision if Dan is busy). A few things inline. All trivial Reviewed-by: Jonathan Cameron > int cxl_dpa_set_part(struct cxl_endpoint_decoder *cxled, > enum cxl_partition_mode mode) > @@ -613,6 +622,82 @@ int cxl_dpa_set_part(struct cxl_endpoint_decoder *cxled, > return 0; > } > > +static int find_free_decoder(struct device *dev, const void *data) > +{ > + struct cxl_endpoint_decoder *cxled; > + struct cxl_port *port; > + > + if (!is_endpoint_decoder(dev)) > + return 0; > + > + cxled = to_cxl_endpoint_decoder(dev); > + port = cxled_to_port(cxled); > + > + return cxled->cxld.id == (port->hdm_end + 1); > +} > + > +static struct cxl_endpoint_decoder * > +cxl_find_free_decoder(struct cxl_memdev *cxlmd) > +{ > + struct cxl_port *endpoint = cxlmd->endpoint; > + struct device *dev; > + > + guard(rwsem_read)(&cxl_rwsem.dpa); > + dev = device_find_child(&endpoint->dev, NULL, > + find_free_decoder); > + if (dev) > + return to_cxl_endpoint_decoder(dev); > + > + return NULL; Trivial but I'd prefer to see the 'error' like thing out of line if (!dev) return NULL; return to_cxl_endpoint_decoder(dev); > +} > + > +/** > + * cxl_request_dpa - search and reserve DPA given input constraints > + * @cxlmd: memdev with an endpoint port with available decoders > + * @mode: CXL partition mode (ram vs pmem) > + * @alloc: dpa size required > + * > + * Returns a pointer to a 'struct cxl_endpoint_decoder' on success or > + * an errno encoded pointer on failure. > + * > + * 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. The expectation is that @alloc is a driver known > + * value based on the device capacity but which could not be fully > + * available due to HPA constraints. > + * > + * Returns a pinned cxl_decoder with at least @alloc 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_memdev *cxlmd, > + enum cxl_partition_mode mode, > + resource_size_t alloc) > +{ > + int rc; > + > + if (!IS_ALIGNED(alloc, SZ_256M)) > + return ERR_PTR(-EINVAL); > + > + struct cxl_endpoint_decoder *cxled __free(put_cxled) = > + cxl_find_free_decoder(cxlmd); > + > + if (!cxled) > + return ERR_PTR(-ENODEV); > + > + rc = cxl_dpa_set_part(cxled, mode); > + if (rc) > + return ERR_PTR(rc); > + > + rc = cxl_dpa_alloc(cxled, alloc); > + if (rc) > + return ERR_PTR(rc); > + > + return no_free_ptr(cxled); return_ptr() (it's exactly the same implementation). > +} > +EXPORT_SYMBOL_NS_GPL(cxl_request_dpa, "CXL");