From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6C322C388F7 for ; Tue, 10 Nov 2020 23:25:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0B92320825 for ; Tue, 10 Nov 2020 23:25:18 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="dPV32dPJ" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732213AbgKJXZS (ORCPT ); Tue, 10 Nov 2020 18:25:18 -0500 Received: from mail.kernel.org ([198.145.29.99]:37548 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731234AbgKJXZQ (ORCPT ); Tue, 10 Nov 2020 18:25:16 -0500 Received: from localhost (230.sub-72-107-127.myvzw.com [72.107.127.230]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id BC9BC20781; Tue, 10 Nov 2020 23:25:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1605050715; bh=o6lMTu5xFOzYsPde49ClXFU1xXCgPh17zPTl4Yx9dys=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=dPV32dPJxAhqlhllWUsMt1gC7dOq85ACuyi2fnWL+r9/kPB0YaAY/q+UhWjLeQo7V ZDoeayJFbRzQ9/aW39itkyKKH8s+us5oMd9a8UfsuIgKpGjmBDN1DXk5OlpCVC2zRi xPJXtoRNKmQs4fail2G1MnvjO16Ve1HVNwPMHkTo= Date: Tue, 10 Nov 2020 17:25:13 -0600 From: Bjorn Helgaas To: Logan Gunthorpe Cc: linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org, linux-block@vger.kernel.org, linux-pci@vger.kernel.org, linux-mm@kvack.org, iommu@lists.linux-foundation.org, Stephen Bates , Christoph Hellwig , Dan Williams , Jason Gunthorpe , Christian =?iso-8859-1?Q?K=F6nig?= , Ira Weiny , John Hubbard , Don Dutile , Matthew Wilcox , Daniel Vetter Subject: Re: [RFC PATCH 03/15] PCI/P2PDMA: Introduce pci_p2pdma_should_map_bus() and pci_p2pdma_bus_offset() Message-ID: <20201110232513.GA705726@bjorn-Precision-5520> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201106170036.18713-4-logang@deltatee.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Nov 06, 2020 at 10:00:24AM -0700, Logan Gunthorpe wrote: > Introduce pci_p2pdma_should_map_bus() which is meant to be called by > dma map functions to determine how to map a given p2pdma page. s/dma/DMA/ for consistency (also below in function comment) > pci_p2pdma_bus_offset() is also added to allow callers to get the bus > offset if they need to map the bus address. > > Signed-off-by: Logan Gunthorpe > --- > drivers/pci/p2pdma.c | 46 ++++++++++++++++++++++++++++++++++++++ > include/linux/pci-p2pdma.h | 11 +++++++++ > 2 files changed, 57 insertions(+) > > diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c > index ea8472278b11..9961e779f430 100644 > --- a/drivers/pci/p2pdma.c > +++ b/drivers/pci/p2pdma.c > @@ -930,6 +930,52 @@ void pci_p2pdma_unmap_sg_attrs(struct device *dev, struct scatterlist *sg, > } > EXPORT_SYMBOL_GPL(pci_p2pdma_unmap_sg_attrs); > > +/** > + * pci_p2pdma_bus_offset - returns the bus offset for a given page > + * @page: page to get the offset for > + * > + * Must be passed a pci p2pdma page. s/pci/PCI/ > + */ > +u64 pci_p2pdma_bus_offset(struct page *page) > +{ > + struct pci_p2pdma_pagemap *p2p_pgmap = to_p2p_pgmap(page->pgmap); > + > + WARN_ON(!is_pci_p2pdma_page(page)); > + > + return p2p_pgmap->bus_offset; > +} > +EXPORT_SYMBOL_GPL(pci_p2pdma_bus_offset); > + > +/** > + * pci_p2pdma_should_map_bus - determine if a dma mapping should use the > + * bus address > + * @dev: device doing the DMA request > + * @pgmap: dev_pagemap structure for the mapping > + * > + * Returns 1 if the page should be mapped with a bus address, 0 otherwise > + * and -1 the device should not be mapping P2PDMA pages. I think this is missing a word. I'm not really sure how to interpret the "should" in pci_p2pdma_should_map_bus(). If this returns -1, does that mean the patches *cannot* be mapped? They *could* be mapped, but you really *shouldn't*? Something else? 1 means page should be mapped with bus address. 0 means ... what, exactly? It should be mapped with some different address? Sorry these are naive questions because I don't know how all this works. > + */ > +int pci_p2pdma_should_map_bus(struct device *dev, struct dev_pagemap *pgmap) > +{ > + struct pci_p2pdma_pagemap *p2p_pgmap = to_p2p_pgmap(pgmap); > + struct pci_dev *client; > + > + if (!dev_is_pci(dev)) > + return -1; > + > + client = to_pci_dev(dev); > + > + switch (pci_p2pdma_map_type(p2p_pgmap->provider, client)) { > + case PCI_P2PDMA_MAP_THRU_HOST_BRIDGE: > + return 0; > + case PCI_P2PDMA_MAP_BUS_ADDR: > + return 1; > + default: > + return -1; > + } > +} > +EXPORT_SYMBOL_GPL(pci_p2pdma_should_map_bus); > + > /** > * pci_p2pdma_enable_store - parse a configfs/sysfs attribute store > * to enable p2pdma > diff --git a/include/linux/pci-p2pdma.h b/include/linux/pci-p2pdma.h > index 8318a97c9c61..fc5de47eeac4 100644 > --- a/include/linux/pci-p2pdma.h > +++ b/include/linux/pci-p2pdma.h > @@ -34,6 +34,8 @@ int pci_p2pdma_map_sg_attrs(struct device *dev, struct scatterlist *sg, > int nents, enum dma_data_direction dir, unsigned long attrs); > void pci_p2pdma_unmap_sg_attrs(struct device *dev, struct scatterlist *sg, > int nents, enum dma_data_direction dir, unsigned long attrs); > +u64 pci_p2pdma_bus_offset(struct page *page); > +int pci_p2pdma_should_map_bus(struct device *dev, struct dev_pagemap *pgmap); > int pci_p2pdma_enable_store(const char *page, struct pci_dev **p2p_dev, > bool *use_p2pdma); > ssize_t pci_p2pdma_enable_show(char *page, struct pci_dev *p2p_dev, > @@ -83,6 +85,15 @@ static inline void pci_p2pmem_free_sgl(struct pci_dev *pdev, > static inline void pci_p2pmem_publish(struct pci_dev *pdev, bool publish) > { > } > +static inline u64 pci_p2pdma_bus_offset(struct page *page) > +{ > + return -1; > +} > +static inline int pci_p2pdma_should_map_bus(struct device *dev, > + struct dev_pagemap *pgmap) > +{ > + return -1; > +} > static inline int pci_p2pdma_map_sg_attrs(struct device *dev, > struct scatterlist *sg, int nents, enum dma_data_direction dir, > unsigned long attrs) > -- > 2.20.1 >