linux-kernel - Re: [PATCH 07/18] dma-mapping: Implement link/unlink ranges API

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Message-ID: <6a9366a5-7c5b-449c-b259-8e2492aae2a1@linux.intel.com>
Date: Mon, 28 Oct 2024 10:00:25 +0800
From: Baolu Lu <baolu.lu@...ux.intel.com>
To: Leon Romanovsky <leon@...nel.org>, Jens Axboe <axboe@...nel.dk>,
 Jason Gunthorpe <jgg@...pe.ca>, Robin Murphy <robin.murphy@....com>,
 Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
 Christoph Hellwig <hch@....de>, Sagi Grimberg <sagi@...mberg.me>
Cc: baolu.lu@...ux.intel.com, Leon Romanovsky <leonro@...dia.com>,
 Keith Busch <kbusch@...nel.org>, 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>,
 Marek Szyprowski <m.szyprowski@...sung.com>,
 Jérôme Glisse <jglisse@...hat.com>,
 Andrew Morton <akpm@...ux-foundation.org>, Jonathan Corbet <corbet@....net>,
 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
Subject: Re: [PATCH 07/18] dma-mapping: Implement link/unlink ranges API

On 2024/10/27 22:21, Leon Romanovsky wrote:
> +/**
> + * dma_iova_sync - Sync IOTLB
> + * @dev: DMA device
> + * @state: IOVA state
> + * @offset: offset into the IOVA state to sync
> + * @size: size of the buffer
> + * @ret: return value from the last IOVA operation
> + *
> + * 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
> + * to sync the IOTLB.
> + */
> +int dma_iova_sync(struct device *dev, struct dma_iova_state *state,
> +		size_t offset, size_t size, int ret)
> +{
> +	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);
> +
> +	addr -= iova_start_pad;
> +	size = iova_align(iovad, size + iova_start_pad);
> +
> +	if (!ret)
> +		ret = iommu_sync_map(domain, addr, size);
> +	if (ret)
> +		iommu_unmap(domain, addr, size);

It appears strange that mapping is not done in this helper, but
unmapping is added in the failure path. Perhaps I overlooked anything?
To my understanding, it should like below:

	return iommu_sync_map(domain, addr, size);

In the drivers that make use of this interface should do something like
below:

	ret = dma_iova_sync(...);
	if (ret)
		dma_iova_destroy(...)

> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(dma_iova_sync);

Thanks,
baolu