Re: [PATCH v9 6/9] tee: add tee_shm_alloc_dma_mem()

[Sumit Garg <sumit.garg@kernel.org>]

On Tue, May 20, 2025 at 05:16:49PM +0200, Jens Wiklander wrote:
> Add tee_shm_alloc_dma_mem() to allocate DMA memory. The memory is
> represented by a tee_shm object using the new flag TEE_SHM_DMA_MEM to
> identify it as DMA memory. The allocated memory will later be lent to
> the TEE to be used as protected memory.
> 
> Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>
> ---
>  drivers/tee/tee_shm.c    | 74 ++++++++++++++++++++++++++++++++++++++--
>  include/linux/tee_core.h |  5 +++
>  2 files changed, 77 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/tee/tee_shm.c b/drivers/tee/tee_shm.c
> index e1ed52ee0a16..92a6a35e1a1e 100644
> --- a/drivers/tee/tee_shm.c
> +++ b/drivers/tee/tee_shm.c
> @@ -5,6 +5,8 @@
>  #include <linux/anon_inodes.h>
>  #include <linux/device.h>
>  #include <linux/dma-buf.h>
> +#include <linux/dma-mapping.h>
> +#include <linux/highmem.h>
>  #include <linux/idr.h>
>  #include <linux/io.h>
>  #include <linux/mm.h>
> @@ -13,9 +15,14 @@
>  #include <linux/tee_core.h>
>  #include <linux/uaccess.h>
>  #include <linux/uio.h>
> -#include <linux/highmem.h>
>  #include "tee_private.h"
>  
> +struct tee_shm_dma_mem {
> +	struct tee_shm shm;
> +	dma_addr_t dma_addr;
> +	struct page *page;
> +};
> +
>  static void shm_put_kernel_pages(struct page **pages, size_t page_count)
>  {
>  	size_t n;
> @@ -49,7 +56,14 @@ static void tee_shm_release(struct tee_device *teedev, struct tee_shm *shm)
>  	struct tee_shm *parent_shm = NULL;
>  	void *p = shm;
>  
> -	if (shm->flags & TEE_SHM_DMA_BUF) {
> +	if (shm->flags & TEE_SHM_DMA_MEM) {
> +		struct tee_shm_dma_mem *dma_mem;
> +
> +		dma_mem = container_of(shm, struct tee_shm_dma_mem, shm);
> +		p = dma_mem;
> +		dma_free_pages(&teedev->dev, shm->size, dma_mem->page,
> +			       dma_mem->dma_addr, DMA_BIDIRECTIONAL);

Although the kernel bot already found a randconfig issue, it looks like
we need to add Kconfig dependencies like HAS_DMA, DMA_CMA etc.

Also, I was thinking if we should rather add a new TEE subsystem
specific Kconfig option like: TEE_DMABUF_HEAPS which can then be used to
select whatever dependency is needed as well as act as a gating Kconfig
for relevant features.

-Sumit

> +	} else if (shm->flags & TEE_SHM_DMA_BUF) {
>  		struct tee_shm_dmabuf_ref *ref;
>  
>  		ref = container_of(shm, struct tee_shm_dmabuf_ref, shm);
> @@ -306,6 +320,62 @@ struct tee_shm *tee_shm_alloc_priv_buf(struct tee_context *ctx, size_t size)
>  }
>  EXPORT_SYMBOL_GPL(tee_shm_alloc_priv_buf);
>  
> +/**
> + * tee_shm_alloc_dma_mem() - Allocate DMA memory as shared memory object
> + * @ctx:	Context that allocates the shared memory
> + * @page_count:	Number of pages
> + *
> + * The allocated memory is expected to be lent (made inaccessible to the
> + * kernel) to the TEE while it's used and returned (accessible to the
> + * kernel again) before it's freed.
> + *
> + * This function should normally only be used internally in the TEE
> + * drivers.
> + *
> + * @returns a pointer to 'struct tee_shm'
> + */
> +struct tee_shm *tee_shm_alloc_dma_mem(struct tee_context *ctx,
> +				      size_t page_count)
> +{
> +	struct tee_device *teedev = ctx->teedev;
> +	struct tee_shm_dma_mem *dma_mem;
> +	dma_addr_t dma_addr;
> +	struct page *page;
> +
> +	if (!tee_device_get(teedev))
> +		return ERR_PTR(-EINVAL);
> +
> +	page = dma_alloc_pages(&teedev->dev, page_count * PAGE_SIZE,
> +			       &dma_addr, DMA_BIDIRECTIONAL, GFP_KERNEL);
> +	if (!page)
> +		goto err_put_teedev;
> +
> +	dma_mem = kzalloc(sizeof(*dma_mem), GFP_KERNEL);
> +	if (!dma_mem)
> +		goto err_free_pages;
> +
> +	refcount_set(&dma_mem->shm.refcount, 1);
> +	dma_mem->shm.ctx = ctx;
> +	dma_mem->shm.paddr = page_to_phys(page);
> +	dma_mem->dma_addr = dma_addr;
> +	dma_mem->page = page;
> +	dma_mem->shm.size = page_count * PAGE_SIZE;
> +	dma_mem->shm.flags = TEE_SHM_DMA_MEM;
> +
> +	teedev_ctx_get(ctx);
> +
> +	return &dma_mem->shm;
> +
> +err_free_pages:
> +	dma_free_pages(&teedev->dev, page_count * PAGE_SIZE, page, dma_addr,
> +		       DMA_BIDIRECTIONAL);
> +err_put_teedev:
> +	tee_device_put(teedev);
> +
> +	return ERR_PTR(-ENOMEM);
> +}
> +EXPORT_SYMBOL_GPL(tee_shm_alloc_dma_mem);
> +
>  int tee_dyn_shm_alloc_helper(struct tee_shm *shm, size_t size, size_t align,
>  			     int (*shm_register)(struct tee_context *ctx,
>  						 struct tee_shm *shm,
> diff --git a/include/linux/tee_core.h b/include/linux/tee_core.h
> index 02c07f661349..925690e1020b 100644
> --- a/include/linux/tee_core.h
> +++ b/include/linux/tee_core.h
> @@ -29,6 +29,8 @@
>  #define TEE_SHM_POOL		BIT(2)  /* Memory allocated from pool */
>  #define TEE_SHM_PRIV		BIT(3)  /* Memory private to TEE driver */
>  #define TEE_SHM_DMA_BUF		BIT(4)	/* Memory with dma-buf handle */
> +#define TEE_SHM_DMA_MEM		BIT(5)	/* Memory allocated with */
> +					/* dma_alloc_pages() */
>  
>  #define TEE_DEVICE_FLAG_REGISTERED	0x1
>  #define TEE_MAX_DEV_NAME_LEN		32
> @@ -310,6 +312,9 @@ void *tee_get_drvdata(struct tee_device *teedev);
>   */
>  struct tee_shm *tee_shm_alloc_priv_buf(struct tee_context *ctx, size_t size);
>  
> +struct tee_shm *tee_shm_alloc_dma_mem(struct tee_context *ctx,
> +				      size_t page_count);
> +
>  int tee_dyn_shm_alloc_helper(struct tee_shm *shm, size_t size, size_t align,
>  			     int (*shm_register)(struct tee_context *ctx,
>  						 struct tee_shm *shm,
> -- 
> 2.43.0
>