From patchwork Thu Sep 16 23:40:41 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Logan Gunthorpe X-Patchwork-Id: 12500571 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=-16.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham 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 542ACC4167E for ; Thu, 16 Sep 2021 23:41:28 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 0D0A761108 for ; Thu, 16 Sep 2021 23:41:28 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 0D0A761108 Authentication-Results: mail.kernel.org; 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dkim=pass header.d=deltatee.com header.s=20200525 header.b=RFVdJzEG; spf=pass (imf17.hostedemail.com: domain of gunthorp@deltatee.com designates 204.191.154.188 as permitted sender) smtp.mailfrom=gunthorp@deltatee.com; dmarc=pass (policy=none) header.from=deltatee.com X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 51D35F00039F X-Stat-Signature: 8szqxa74nue5ion5u3hmekry8hwggoc7 X-HE-Tag: 1631835674-839113 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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 P2PDMA. Using this bit requires adding an additional dependency on CONFIG_64BIT to CONFIG_PCI_P2PDMA. 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: John Hubbard Reviewed-by: Jason Gunthorpe Reviewed-by: Chaitanya Kulkarni --- drivers/pci/Kconfig | 2 +- include/linux/scatterlist.h | 50 ++++++++++++++++++++++++++++++++++--- 2 files changed, 47 insertions(+), 5 deletions(-) diff --git a/drivers/pci/Kconfig b/drivers/pci/Kconfig index 0c473d75e625..90b4bddb3300 100644 --- a/drivers/pci/Kconfig +++ b/drivers/pci/Kconfig @@ -163,7 +163,7 @@ config PCI_PASID config PCI_P2PDMA bool "PCI peer-to-peer transfer support" - depends on ZONE_DEVICE + depends on ZONE_DEVICE && 64BIT 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 266754a55327..e62b1cf6386f 100644 --- a/include/linux/scatterlist.h +++ b/include/linux/scatterlist.h @@ -64,6 +64,21 @@ 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 PCI + * bus address when doing P2PDMA. + * Note: CONFIG_PCI_P2PDMA depends on CONFIG_64BIT because of this. + */ + +#ifdef CONFIG_PCI_P2PDMA +#define SG_DMA_PCI_P2PDMA 0x04UL +#else +#define SG_DMA_PCI_P2PDMA 0x00UL +#endif + +#define SG_PAGE_LINK_MASK (SG_CHAIN | SG_END | SG_DMA_PCI_P2PDMA) + /* * 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. @@ -72,7 +87,9 @@ struct sg_append_table { #define sg_is_chain(sg) ((sg)->page_link & SG_CHAIN) #define sg_is_last(sg) ((sg)->page_link & SG_END) #define sg_chain_ptr(sg) \ - ((struct scatterlist *) ((sg)->page_link & ~(SG_CHAIN | SG_END))) + ((struct scatterlist *)((sg)->page_link & ~SG_PAGE_LINK_MASK)) + +#define sg_is_dma_pci_p2pdma(sg) ((sg)->page_link & SG_DMA_PCI_P2PDMA) /** * sg_assign_page - Assign a given page to an SG entry @@ -86,13 +103,13 @@ struct sg_append_table { **/ static inline void sg_assign_page(struct scatterlist *sg, struct page *page) { - unsigned long page_link = sg->page_link & (SG_CHAIN | SG_END); + unsigned long page_link = sg->page_link & SG_PAGE_LINK_MASK; /* * In order for the low bit stealing approach to work, pages * must be aligned at a 32-bit boundary as a minimum. */ - BUG_ON((unsigned long) page & (SG_CHAIN | SG_END)); + BUG_ON((unsigned long)page & SG_PAGE_LINK_MASK); #ifdef CONFIG_DEBUG_SG BUG_ON(sg_is_chain(sg)); #endif @@ -126,7 +143,7 @@ static inline struct page *sg_page(struct scatterlist *sg) #ifdef CONFIG_DEBUG_SG BUG_ON(sg_is_chain(sg)); #endif - return (struct page *)((sg)->page_link & ~(SG_CHAIN | SG_END)); + return (struct page *)((sg)->page_link & ~SG_PAGE_LINK_MASK); } /** @@ -228,6 +245,31 @@ static inline void sg_unmark_end(struct scatterlist *sg) sg->page_link &= ~SG_END; } +/** + * sg_dma_mark_pci_p2pdma - Mark the scatterlist entry for PCI p2pdma + * @sg: SG entryScatterlist + * + * Description: + * Marks the passed in sg entry to indicate that the dma_address is + * a PCI bus address. + **/ +static inline void sg_dma_mark_pci_p2pdma(struct scatterlist *sg) +{ + sg->page_link |= SG_DMA_PCI_P2PDMA; +} + +/** + * sg_unmark_pci_p2pdma - Unmark the scatterlist entry for PCI p2pdma + * @sg: SG entryScatterlist + * + * Description: + * Clears the PCI P2PDMA mark + **/ +static inline void sg_dma_unmark_pci_p2pdma(struct scatterlist *sg) +{ + sg->page_link &= ~SG_DMA_PCI_P2PDMA; +} + /** * sg_phys - Return physical address of an sg entry * @sg: SG entry