From patchwork Fri May 20 08:23:20 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: John Garry X-Patchwork-Id: 575706 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 85F32C433FE for ; Fri, 20 May 2022 08:29:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1347023AbiETI3l (ORCPT ); Fri, 20 May 2022 04:29:41 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39400 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1346992AbiETI3b (ORCPT ); Fri, 20 May 2022 04:29:31 -0400 Received: from frasgout.his.huawei.com (frasgout.his.huawei.com [185.176.79.56]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E70AE42A21; Fri, 20 May 2022 01:29:29 -0700 (PDT) Received: from fraeml710-chm.china.huawei.com (unknown [172.18.147.201]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4L4KYF06pRz687t6; Fri, 20 May 2022 16:25:37 +0800 (CST) Received: from lhreml724-chm.china.huawei.com (10.201.108.75) by fraeml710-chm.china.huawei.com (10.206.15.59) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Fri, 20 May 2022 10:29:27 +0200 Received: from localhost.localdomain (10.69.192.58) by lhreml724-chm.china.huawei.com (10.201.108.75) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Fri, 20 May 2022 09:29:24 +0100 From: John Garry To: , , , , , , , CC: , , , , , , , , John Garry Subject: [PATCH 1/4] dma-mapping: Add dma_opt_mapping_size() Date: Fri, 20 May 2022 16:23:20 +0800 Message-ID: <1653035003-70312-2-git-send-email-john.garry@huawei.com> X-Mailer: git-send-email 2.8.1 In-Reply-To: <1653035003-70312-1-git-send-email-john.garry@huawei.com> References: <1653035003-70312-1-git-send-email-john.garry@huawei.com> MIME-Version: 1.0 X-Originating-IP: [10.69.192.58] X-ClientProxiedBy: dggems701-chm.china.huawei.com (10.3.19.178) To lhreml724-chm.china.huawei.com (10.201.108.75) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org Streaming DMA mapping involving an IOMMU may be much slower for larger total mapping size. This is because every IOMMU DMA mapping requires an IOVA to be allocated and freed. IOVA sizes above a certain limit are not cached, which can have a big impact on DMA mapping performance. Provide an API for device drivers to know this "optimal" limit, such that they may try to produce mapping which don't exceed it. Signed-off-by: John Garry --- Documentation/core-api/dma-api.rst | 9 +++++++++ include/linux/dma-map-ops.h | 1 + include/linux/dma-mapping.h | 5 +++++ kernel/dma/mapping.c | 12 ++++++++++++ 4 files changed, 27 insertions(+) diff --git a/Documentation/core-api/dma-api.rst b/Documentation/core-api/dma-api.rst index 6d6d0edd2d27..b3cd9763d28b 100644 --- a/Documentation/core-api/dma-api.rst +++ b/Documentation/core-api/dma-api.rst @@ -204,6 +204,15 @@ Returns the maximum size of a mapping for the device. The size parameter of the mapping functions like dma_map_single(), dma_map_page() and others should not be larger than the returned value. +:: + + size_t + dma_opt_mapping_size(struct device *dev); + +Returns the maximum optimal size of a mapping for the device. Mapping large +buffers may take longer so device drivers are advised to limit total DMA +streaming mappings length to the returned value. + :: bool diff --git a/include/linux/dma-map-ops.h b/include/linux/dma-map-ops.h index 0d5b06b3a4a6..98ceba6fa848 100644 --- a/include/linux/dma-map-ops.h +++ b/include/linux/dma-map-ops.h @@ -69,6 +69,7 @@ struct dma_map_ops { int (*dma_supported)(struct device *dev, u64 mask); u64 (*get_required_mask)(struct device *dev); size_t (*max_mapping_size)(struct device *dev); + size_t (*opt_mapping_size)(void); unsigned long (*get_merge_boundary)(struct device *dev); }; diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h index dca2b1355bb1..fe3849434b2a 100644 --- a/include/linux/dma-mapping.h +++ b/include/linux/dma-mapping.h @@ -144,6 +144,7 @@ int dma_set_mask(struct device *dev, u64 mask); int dma_set_coherent_mask(struct device *dev, u64 mask); u64 dma_get_required_mask(struct device *dev); size_t dma_max_mapping_size(struct device *dev); +size_t dma_opt_mapping_size(struct device *dev); bool dma_need_sync(struct device *dev, dma_addr_t dma_addr); unsigned long dma_get_merge_boundary(struct device *dev); struct sg_table *dma_alloc_noncontiguous(struct device *dev, size_t size, @@ -266,6 +267,10 @@ static inline size_t dma_max_mapping_size(struct device *dev) { return 0; } +static inline size_t dma_opt_mapping_size(struct device *dev) +{ + return 0; +} static inline bool dma_need_sync(struct device *dev, dma_addr_t dma_addr) { return false; diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c index db7244291b74..1bfe11b1edb6 100644 --- a/kernel/dma/mapping.c +++ b/kernel/dma/mapping.c @@ -773,6 +773,18 @@ size_t dma_max_mapping_size(struct device *dev) } EXPORT_SYMBOL_GPL(dma_max_mapping_size); +size_t dma_opt_mapping_size(struct device *dev) +{ + const struct dma_map_ops *ops = get_dma_ops(dev); + size_t size = SIZE_MAX; + + if (ops && ops->opt_mapping_size) + size = ops->opt_mapping_size(); + + return min(dma_max_mapping_size(dev), size); +} +EXPORT_SYMBOL_GPL(dma_opt_mapping_size); + bool dma_need_sync(struct device *dev, dma_addr_t dma_addr) { const struct dma_map_ops *ops = get_dma_ops(dev);