linux-kernel - Re: [PATCH] iommufd: fix building without dmabuf

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Message-ID: <20251204131205.GM812105@ziepe.ca>
Date: Thu, 4 Dec 2025 09:12:05 -0400
From: Jason Gunthorpe <jgg@...pe.ca>
To: Arnd Bergmann <arnd@...nel.org>
Cc: Kevin Tian <kevin.tian@...el.com>, Joerg Roedel <joro@...tes.org>,
	Will Deacon <will@...nel.org>, Nicolin Chen <nicolinc@...dia.com>,
	Arnd Bergmann <arnd@...db.de>, Robin Murphy <robin.murphy@....com>,
	Lu Baolu <baolu.lu@...ux.intel.com>, Alex Mastro <amastro@...com>,
	iommu@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iommufd: fix building without dmabuf

On Thu, Dec 04, 2025 at 11:03:29AM +0100, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@...db.de>
> 
> When DMABUF is disabled, trying to use it causes a link failure:
> 
> x86_64-linux-ld: drivers/iommu/iommufd/io_pagetable.o: in function `iopt_map_file_pages':
> io_pagetable.c:(.text+0x1735): undefined reference to `dma_buf_get'
> x86_64-linux-ld: io_pagetable.c:(.text+0x1775): undefined reference to `dma_buf_put'
> 
> Fixes: 44ebaa1744fd ("iommufd: Accept a DMABUF through IOMMU_IOAS_MAP_FILE")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  drivers/iommu/iommufd/io_pagetable.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/iommu/iommufd/io_pagetable.c b/drivers/iommu/iommufd/io_pagetable.c
> index 54cf4d856179..d22e86de03e9 100644
> --- a/drivers/iommu/iommufd/io_pagetable.c
> +++ b/drivers/iommu/iommufd/io_pagetable.c
> @@ -495,7 +495,11 @@ int iopt_map_file_pages(struct iommufd_ctx *ictx, struct io_pagetable *iopt,
>  		return -EOVERFLOW;
>  
>  	start_byte = start - ALIGN_DOWN(start, PAGE_SIZE);
> -	dmabuf = dma_buf_get(fd);
> +	if (IS_ENABLED(CONFIG_DMABUF_HEAPS))
> +		dmabuf = dma_buf_get(fd);
> +	else
> +		dmabuf = ERR_PTR(-ENXIO);

Shouldn't this be fixed in include/linux/dma-buf.h with a stub always
fail inline?

Jason