From patchwork Wed Nov 17 21:53:49 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Logan Gunthorpe X-Patchwork-Id: 12625499 X-Patchwork-Delegate: bhelgaas@google.com 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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 59DBAC433F5 for ; Wed, 17 Nov 2021 21:54:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4243561BCF for ; Wed, 17 Nov 2021 21:54:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240968AbhKQV5g (ORCPT ); Wed, 17 Nov 2021 16:57:36 -0500 Received: from ale.deltatee.com ([204.191.154.188]:58734 "EHLO ale.deltatee.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240843AbhKQV5Y (ORCPT ); Wed, 17 Nov 2021 16:57:24 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=deltatee.com; s=20200525; h=Subject:MIME-Version:References:In-Reply-To: Message-Id:Date:Cc:To:From:content-disposition; bh=E9tQWtvaLICmPSoEVBJb4KTrJ+PSjHquPVLYmy++lAQ=; b=mxEXmW4OZEo8i67U5DMx5HrPbS AK51pgfhmTpE6vjIujjmCpY6A999ck0das6Npk9wDVBcYvnl0gbK1ZiUDlXCosy+XmIlbhUrVTAPZ 91/bA6ba3/Cvv04qAIODBzWTtAiiSx+V26PZJhQnAs12eMgjW7W09G8nDZ3Grj/zcNnkBFe16y2/x 3EeSCU5zQmKpyIBKL3ExEDIK8vyuN11OYMSzAtVXOmO6g9WGvL2RbrJQUL8n8Bi1fVrHh4w1bx0ZC jvYm0EPPRg8+gcnpY5++dLLNcWVdibi79wrXO38JGd6xsQRZfLh0GmriWFh1BXBlkfAKoiPIIxUux I8dRAKeA==; Received: from cgy1-donard.priv.deltatee.com ([172.16.1.31]) by ale.deltatee.com with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1mnSsi-000Zo5-TA; Wed, 17 Nov 2021 14:54:17 -0700 Received: from gunthorp by cgy1-donard.priv.deltatee.com with local (Exim 4.94.2) (envelope-from ) id 1mnSse-0000yr-90; Wed, 17 Nov 2021 14:54:12 -0700 From: Logan Gunthorpe To: 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 Cc: Stephen Bates , Christoph Hellwig , Dan Williams , Jason Gunthorpe , =?utf-8?q?Christian_K=C3=B6nig?= , John Hubbard , Don Dutile , Matthew Wilcox , Daniel Vetter , Jakowski Andrzej , Minturn Dave B , Jason Ekstrand , Dave Hansen , Xiong Jianxin , Bjorn Helgaas , Ira Weiny , Robin Murphy , Martin Oliveira , Chaitanya Kulkarni , Logan Gunthorpe Date: Wed, 17 Nov 2021 14:53:49 -0700 Message-Id: <20211117215410.3695-3-logang@deltatee.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20211117215410.3695-1-logang@deltatee.com> References: <20211117215410.3695-1-logang@deltatee.com> MIME-Version: 1.0 X-SA-Exim-Connect-IP: 172.16.1.31 X-SA-Exim-Rcpt-To: linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, linux-pci@vger.kernel.org, linux-mm@kvack.org, iommu@lists.linux-foundation.org, sbates@raithlin.com, hch@lst.de, jgg@ziepe.ca, christian.koenig@amd.com, jhubbard@nvidia.com, ddutile@redhat.com, willy@infradead.org, daniel.vetter@ffwll.ch, jason@jlekstrand.net, dave.hansen@linux.intel.com, helgaas@kernel.org, dan.j.williams@intel.com, andrzej.jakowski@intel.com, dave.b.minturn@intel.com, jianxin.xiong@intel.com, ira.weiny@intel.com, robin.murphy@arm.com, martin.oliveira@eideticom.com, ckulkarnilinux@gmail.com, logang@deltatee.com X-SA-Exim-Mail-From: gunthorp@deltatee.com Subject: [PATCH v4 02/23] lib/scatterlist: add flag for indicating P2PDMA segments in an SGL X-SA-Exim-Version: 4.2.1 (built Sat, 13 Feb 2021 17:57:42 +0000) X-SA-Exim-Scanned: Yes (on ale.deltatee.com) Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org Make use of the third free LSB in scatterlist's page_link on 64bit systems. The extra bit will be used by dma_[un]map_sg_p2pdma() to determine when a given SGL segments dma_address points to a PCI bus address. dma_unmap_sg_p2pdma() will need to perform different cleanup when a segment is marked as a bus address. Create a CONFIG_NEED_SG_DMA_BUS_ADDR_FLAG bool which depends on CONFIG_64BIT (so there is space in the page link for the new flag). CONFIG_PCI_P2PDMA will then depend on this so this means PCI P2PDMA will require CONFIG_64BIT. This should be acceptable as the majority of P2PDMA use cases are restricted to newer root complexes and roughly require the extra address space for memory BARs used in the transactions. Signed-off-by: Logan Gunthorpe Reviewed-by: Chaitanya Kulkarni --- drivers/pci/Kconfig | 5 +++++ include/linux/scatterlist.h | 44 ++++++++++++++++++++++++++++++++++++- kernel/dma/Kconfig | 10 +++++++++ 3 files changed, 58 insertions(+), 1 deletion(-) diff --git a/drivers/pci/Kconfig b/drivers/pci/Kconfig index 43e615aa12ff..95f29601a4df 100644 --- a/drivers/pci/Kconfig +++ b/drivers/pci/Kconfig @@ -164,6 +164,11 @@ config PCI_PASID config PCI_P2PDMA bool "PCI peer-to-peer transfer support" depends on ZONE_DEVICE + # + # The need for the scatterlist DMA bus address flag means PCI P2PDMA + # requires 64bit + # + select NEED_SG_DMA_BUS_ADDR_FLAG select GENERIC_ALLOCATOR help Enableѕ drivers to do PCI peer-to-peer transactions to and from diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h index 7ff9d6386c12..917c09dcc566 100644 --- a/include/linux/scatterlist.h +++ b/include/linux/scatterlist.h @@ -64,12 +64,24 @@ struct sg_append_table { #define SG_CHAIN 0x01UL #define SG_END 0x02UL +/* + * bit 2 is the third free bit in the page_link on 64bit systems which + * is used by dma_unmap_sg() to determine if the dma_address is a + * bus address when doing P2PDMA. + */ +#ifdef CONFIG_NEED_SG_DMA_BUS_ADDR_FLAG +#define SG_DMA_BUS_ADDRESS 0x04UL +static_assert(__alignof__(struct page) >= 8); +#else +#define SG_DMA_BUS_ADDRESS 0x00UL +#endif + /* * We overload the LSB of the page pointer to indicate whether it's * a valid sg entry, or whether it points to the start of a new scatterlist. * Those low bits are there for everyone! (thanks mason :-) */ -#define SG_PAGE_LINK_MASK (SG_CHAIN | SG_END) +#define SG_PAGE_LINK_MASK (SG_CHAIN | SG_END | SG_DMA_BUS_ADDRESS) static inline unsigned int __sg_flags(struct scatterlist *sg) { @@ -91,6 +103,11 @@ static inline bool sg_is_last(struct scatterlist *sg) return __sg_flags(sg) & SG_END; } +static inline bool sg_is_dma_bus_address(struct scatterlist *sg) +{ + return __sg_flags(sg) & SG_DMA_BUS_ADDRESS; +} + /** * sg_assign_page - Assign a given page to an SG entry * @sg: SG entry @@ -245,6 +262,31 @@ static inline void sg_unmark_end(struct scatterlist *sg) sg->page_link &= ~SG_END; } +/** + * sg_dma_mark_bus address - Mark the scatterlist entry as a bus address + * @sg: SG entryScatterlist + * + * Description: + * Marks the passed in sg entry to indicate that the dma_address is + * a bus address and doesn't need to be unmapped. + **/ +static inline void sg_dma_mark_bus_address(struct scatterlist *sg) +{ + sg->page_link |= SG_DMA_BUS_ADDRESS; +} + +/** + * sg_unmark_pci_p2pdma - Unmark the scatterlist entry as a bus address + * @sg: SG entryScatterlist + * + * Description: + * Clears the bus address mark. + **/ +static inline void sg_dma_unmark_bus_address(struct scatterlist *sg) +{ + sg->page_link &= ~SG_DMA_BUS_ADDRESS; +} + /** * sg_phys - Return physical address of an sg entry * @sg: SG entry diff --git a/kernel/dma/Kconfig b/kernel/dma/Kconfig index 1b02179758cb..6e5e1d8e1329 100644 --- a/kernel/dma/Kconfig +++ b/kernel/dma/Kconfig @@ -27,6 +27,16 @@ config ARCH_HAS_DMA_MAP_DIRECT config NEED_SG_DMA_LENGTH bool +# +# PCI P2PDMA needs to store bus addresses in the SGL's dma_address so that the +# dma_unmap_sg() implementations can know not to unmap those segments. +# The flag is stored in the 3rd bit in the page_link field in the SGL +# which means this can only be done on 64bit systems. +# +config NEED_SG_DMA_BUS_ADDR_FLAG + depends on 64BIT + bool + config NEED_DMA_MAP_STATE bool