linux-kernel - Re: [PATCH v8 07/24] dma-mapping: Implement link/unlink ranges API

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Message-ID: <76ac1e9d-b309-4553-b3a9-99674981a06f@oracle.com>
Date: Mon, 21 Apr 2025 01:53:12 +0530
From: ALOK TIWARI <alok.a.tiwari@...cle.com>
To: Leon Romanovsky <leon@...nel.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Jens Axboe <axboe@...nel.dk>, Christoph Hellwig <hch@....de>,
        Keith Busch <kbusch@...nel.org>
Cc: Leon Romanovsky <leonro@...dia.com>, Jake Edge <jake@....net>,
        Jonathan Corbet <corbet@....net>, Jason Gunthorpe <jgg@...pe.ca>,
        Zhu Yanjun <zyjzyj2000@...il.com>, Robin Murphy <robin.murphy@....com>,
        Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        Sagi Grimberg <sagi@...mberg.me>, Bjorn Helgaas <bhelgaas@...gle.com>,
        Logan Gunthorpe <logang@...tatee.com>,
        Yishai Hadas <yishaih@...dia.com>,
        Shameer Kolothum <shameerali.kolothum.thodi@...wei.com>,
        Kevin Tian <kevin.tian@...el.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        Jérôme Glisse <jglisse@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-block@...r.kernel.org,
        linux-rdma@...r.kernel.org, iommu@...ts.linux.dev,
        linux-nvme@...ts.infradead.org, linux-pci@...r.kernel.org,
        kvm@...r.kernel.org, linux-mm@...ck.org,
        Niklas Schnelle <schnelle@...ux.ibm.com>,
        Chuck Lever <chuck.lever@...cle.com>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Matthew Wilcox <willy@...radead.org>,
        Dan Williams
 <dan.j.williams@...el.com>,
        Kanchan Joshi <joshi.k@...sung.com>,
        Chaitanya Kulkarni <kch@...dia.com>
Subject: Re: [PATCH v8 07/24] dma-mapping: Implement link/unlink ranges API


Since we're touching this code, it might be a good opportunity to fix 
the old typo

> + * dma_iova_link - Link a range of IOVA space
> + * @dev: DMA device
> + * @state: IOVA state
> + * @phys: physical address to link
> + * @offset: offset into the IOVA state to map into
> + * @size: size of the buffer
> + * @dir: DMA direction
> + * @attrs: attributes of mapping properties
> + *
> + * Link a range of IOVA space for the given IOVA state without IOTLB sync.
> + * This function is used to link multiple physical addresses in contigueous

old typo contigueous -> contiguous

> + * IOVA space without performing costly IOTLB sync.
> + *
> + * The caller is responsible to call to dma_iova_sync() to sync IOTLB at
> + * the end of linkage.
> + */
> +int dma_iova_link(struct device *dev, struct dma_iova_state *state,
> +		phys_addr_t phys, size_t offset, size_t size,
> +		enum dma_data_direction dir, unsigned long attrs)
> +{
> +	struct iommu_domain *domain = iommu_get_dma_domain(dev);
> +	struct iommu_dma_cookie *cookie = domain->iova_cookie;
> +	struct iova_domain *iovad = &cookie->iovad;
> +	size_t iova_start_pad = iova_offset(iovad, phys);
> +
> +	if (WARN_ON_ONCE(iova_start_pad && offset > 0))
> +		return -EIO;
> +
> +	if (dev_use_swiotlb(dev, size, dir) && iova_offset(iovad, phys | size))
> +		return iommu_dma_iova_link_swiotlb(dev, state, phys, offset,
> +				size, dir, attrs);
> +
> +	return __dma_iova_link(dev, state->addr + offset - iova_start_pad,
> +			phys - iova_start_pad,
> +			iova_align(iovad, size + iova_start_pad), dir, attrs);
> +}
> +EXPORT_SYMBOL_GPL(dma_iova_link);
> +
> +/**
> + * dma_iova_sync - Sync IOTLB
> + * @dev: DMA device
> + * @state: IOVA state
> + * @offset: offset into the IOVA state to sync
> + * @size: size of the buffer
> + *
> + * Sync IOTLB for the given IOVA state. This function should be called on
> + * the IOVA-contigous range created by one ore more dma_iova_link() calls

old typo IOVA-contigous -> IOVA-contiguous

> + * to sync the IOTLB.
> + */
> +int dma_iova_sync(struct device *dev, struct dma_iova_state *state,
> +		size_t offset, size_t size)
> +{
> +	struct iommu_domain *domain = iommu_get_dma_domain(dev);
> +	struct iommu_dma_cookie *cookie = domain->iova_cookie;
> +	struct iova_domain *iovad = &cookie->iovad;
> +	dma_addr_t addr = state->addr + offset;
> +	size_t iova_start_pad = iova_offset(iovad, addr);
> +
> +	return iommu_sync_map(domain, addr - iova_start_pad,
> +		      iova_align(iovad, size + iova_start_pad));
> +}


Thanks,
Alok