[PATCH] iommufd: fix building without dmabuf

[PATCH] iommufd: fix building without dmabuf

[Arnd Bergmann]

From: Arnd Bergmann <arnd@arndb.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@arndb.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);
+
 	if (!IS_ERR(dmabuf)) {
 		pages = iopt_alloc_dmabuf_pages(ictx, dmabuf, start_byte, start,
 						length,
-- 
2.39.5

Re: [PATCH] iommufd: fix building without dmabuf

[Jason Gunthorpe]

On Thu, Dec 04, 2025 at 11:03:29AM +0100, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@arndb.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@arndb.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

Re: [PATCH] iommufd: fix building without dmabuf

[Jason Gunthorpe]

On Thu, Dec 04, 2025 at 11:03:29AM +0100, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@arndb.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@arndb.de>
> ---
>  drivers/iommu/iommufd/io_pagetable.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)

I picked this up anyhow since it looked like adding #ifdef stubs to
dma_buf.h was going to be a bigger thing

> +	if (IS_ENABLED(CONFIG_DMABUF_HEAPS))
> +		dmabuf = dma_buf_get(fd);

But this needs to be:

	if (IS_ENABLED(CONFIG_DMA_SHARED_BUFFER))
		dmabuf = dma_buf_get(fd);

I fixed it

Thanks,
Jason

Re: [PATCH] iommufd: fix building without dmabuf

[Arnd Bergmann]

On Fri, Dec 5, 2025, at 20:50, Jason Gunthorpe wrote:
>
> I picked this up anyhow since it looked like adding #ifdef stubs to
> dma_buf.h was going to be a bigger thing
>
>> +	if (IS_ENABLED(CONFIG_DMABUF_HEAPS))
>> +		dmabuf = dma_buf_get(fd);
>
> But this needs to be:
>
> 	if (IS_ENABLED(CONFIG_DMA_SHARED_BUFFER))
> 		dmabuf = dma_buf_get(fd);
>
> I fixed it

Ok, thanks a lot!

      Arnd