linux-kernel - Re: [PATCH 2/2] dma: Add IOMMU static calls with clear default ops

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Message-ID: <20240711172713.GA1815706@unreal>
Date: Thu, 11 Jul 2024 20:27:13 +0300
From: Leon Romanovsky <leon@...nel.org>
To: Christoph Hellwig <hch@....de>, Robin Murphy <robin.murphy@....com>,
	Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Jason Gunthorpe <jgg@...dia.com>
Cc: linux-kernel@...r.kernel.org, iommu@...ts.linux.dev
Subject: Re: [PATCH 2/2] dma: Add IOMMU static calls with clear default ops

On Thu, Jul 11, 2024 at 01:38:55PM +0300, Leon Romanovsky wrote:
> From: Leon Romanovsky <leonro@...dia.com>
> 
> Most of the IOMMU drivers are using the same DMA operations, which are
> default ones implemented in drivers/iomem/dma-iomem.c. So it makes sense
> to properly set them as a default with direct call without need to
> perform function pointer dereference.
> 
> During system initialization, the IOMMU driver can set its own DMA and
> in such case, the default DMA operations will be overridden.
> 
> Signed-off-by: Leon Romanovsky <leonro@...dia.com>
> ---
>  MAINTAINERS               |  1 +
>  drivers/iommu/dma-iommu.c | 24 +++++++-------
>  include/linux/iommu-dma.h | 50 +++++++++++++++++++++++++++++
>  kernel/dma/iommu.h        | 67 +++++++++++++++++++++++++++++++++++++++
>  kernel/dma/mapping.c      |  9 +++---
>  5 files changed, 134 insertions(+), 17 deletions(-)
>  create mode 100644 include/linux/iommu-dma.h
>  create mode 100644 kernel/dma/iommu.h

<...>

> +++ b/include/linux/iommu-dma.h
> @@ -0,0 +1,50 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Copyright (c) 2024, NVIDIA CORPORATION & AFFILIATES. All rights reserved
> + *
> + * DMA operations that map physical memory through IOMMU.
> + */
> +#ifndef _LINUX_IOMMU_DMA_H
> +#define _LINUX_IOMMU_DMA_H
> +
> +#include <linux/dma-direction.h>
> +
> +#ifdef CONFIG_IOMMU_API

This should be CONFIG_IOMMU_DMA.

diff --git a/include/linux/iommu-dma.h b/include/linux/iommu-dma.h
index b42487bf8f8e..bfdcc9d65daf 100644
--- a/include/linux/iommu-dma.h
+++ b/include/linux/iommu-dma.h
@@ -9,7 +9,7 @@

 #include <linux/dma-direction.h>

-#ifdef CONFIG_IOMMU_API
+#ifdef CONFIG_IOMMU_DMA
 dma_addr_t iommu_dma_map_page(struct device *dev, struct page *page,
                              unsigned long offset, size_t size,
                              enum dma_data_direction dir, unsigned long attrs);
@@ -46,5 +46,5 @@ static void iommu_dma_unmap_sg(struct device *dev, struct scatterlist *sg,
                               unsigned long attrs)
 {
 }
-#endif /* CONFIG_IOMMU_API */
+#endif /* CONFIG_IOMMU_DMA */
 #endif /* _LINUX_IOMMU_DMA_H */

Thanks