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Date: Wed, 31 Jan 2024 14:53:43 +0100
From: Joakim Bech <joakim.bech@linaro.org>
To: Yong Wu <yong.wu@mediatek.com>
Cc: Rob Herring <robh+dt@kernel.org>,
	Matthias Brugger <matthias.bgg@gmail.com>, christian.koenig@amd.com,
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Subject: Re: [PATCH v4 3/7] dma-buf: heaps: restricted_heap: Add private heap
 ops
Message-ID: <20240131135343.rj6xlch6zcev2v47@pop-os.localdomain>
References: <20240112092014.23999-1-yong.wu@mediatek.com>
 <20240112092014.23999-4-yong.wu@mediatek.com>
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In-Reply-To: <20240112092014.23999-4-yong.wu@mediatek.com>

On Fri, Jan 12, 2024 at 05:20:10PM +0800, Yong Wu wrote:
> Add "struct restricted_heap_ops". For the restricted memory, totally there
> are two steps:
> a) memory_alloc: Allocate the buffer in kernel;
> b) memory_restrict: Restrict/Protect/Secure that buffer.
> The memory_alloc is mandatory while memory_restrict is optinal since it may
>
s/optinal/optional/

> be part of memory_alloc.
> 
> Signed-off-by: Yong Wu <yong.wu@mediatek.com>
> ---
>  drivers/dma-buf/heaps/restricted_heap.c | 41 ++++++++++++++++++++++++-
>  drivers/dma-buf/heaps/restricted_heap.h | 12 ++++++++
>  2 files changed, 52 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/dma-buf/heaps/restricted_heap.c b/drivers/dma-buf/heaps/restricted_heap.c
> index fd7c82abd42e..8c266a0f6192 100644
> --- a/drivers/dma-buf/heaps/restricted_heap.c
> +++ b/drivers/dma-buf/heaps/restricted_heap.c
> @@ -12,10 +12,44 @@
>  
>  #include "restricted_heap.h"
>  
> +static int
> +restricted_heap_memory_allocate(struct restricted_heap *heap, struct restricted_buffer *buf)
> +{
> +	const struct restricted_heap_ops *ops = heap->ops;
> +	int ret;
> +
> +	ret = ops->memory_alloc(heap, buf);
> +	if (ret)
> +		return ret;
> +
> +	if (ops->memory_restrict) {
> +		ret = ops->memory_restrict(heap, buf);
> +		if (ret)
> +			goto memory_free;
> +	}
> +	return 0;
> +
> +memory_free:
> +	ops->memory_free(heap, buf);
> +	return ret;
> +}
> +
> +static void
> +restricted_heap_memory_free(struct restricted_heap *heap, struct restricted_buffer *buf)
> +{
> +	const struct restricted_heap_ops *ops = heap->ops;
> +
> +	if (ops->memory_unrestrict)
> +		ops->memory_unrestrict(heap, buf);
> +
> +	ops->memory_free(heap, buf);
> +}
> +
>  static struct dma_buf *
>  restricted_heap_allocate(struct dma_heap *heap, unsigned long size,
>  			 unsigned long fd_flags, unsigned long heap_flags)
>  {
> +	struct restricted_heap *restricted_heap = dma_heap_get_drvdata(heap);
>  	struct restricted_buffer *restricted_buf;
>  	DEFINE_DMA_BUF_EXPORT_INFO(exp_info);
>  	struct dma_buf *dmabuf;
> @@ -28,6 +62,9 @@ restricted_heap_allocate(struct dma_heap *heap, unsigned long size,
>  	restricted_buf->size = ALIGN(size, PAGE_SIZE);
>  	restricted_buf->heap = heap;
>  
> +	ret = restricted_heap_memory_allocate(restricted_heap, restricted_buf);
>
Can we guarantee that "restricted_heap" here isn't NULL (i.e., heap->priv). If
not perhaps we should consider adding a check for NULL in the
restricted_heap_memory_allocate() function?

> +	if (ret)
> +		goto err_free_buf;
>  	exp_info.exp_name = dma_heap_get_name(heap);
>  	exp_info.size = restricted_buf->size;
>  	exp_info.flags = fd_flags;
> @@ -36,11 +73,13 @@ restricted_heap_allocate(struct dma_heap *heap, unsigned long size,
>  	dmabuf = dma_buf_export(&exp_info);
>  	if (IS_ERR(dmabuf)) {
>  		ret = PTR_ERR(dmabuf);
> -		goto err_free_buf;
> +		goto err_free_restricted_mem;
>  	}
>  
>  	return dmabuf;
>  
> +err_free_restricted_mem:
> +	restricted_heap_memory_free(restricted_heap, restricted_buf);
>  err_free_buf:
>  	kfree(restricted_buf);
>  	return ERR_PTR(ret);
> diff --git a/drivers/dma-buf/heaps/restricted_heap.h b/drivers/dma-buf/heaps/restricted_heap.h
> index 443028f6ba3b..ddeaf9805708 100644
> --- a/drivers/dma-buf/heaps/restricted_heap.h
> +++ b/drivers/dma-buf/heaps/restricted_heap.h
> @@ -15,6 +15,18 @@ struct restricted_buffer {
>  
>  struct restricted_heap {
>  	const char		*name;
> +
> +	const struct restricted_heap_ops *ops;
> +};
> +
> +struct restricted_heap_ops {
>
This have the same name as used for the dma_heap_ops in the file
restricted_heap.c, this might be a little bit confusing, or?

> +	int	(*heap_init)(struct restricted_heap *heap);
> +
> +	int	(*memory_alloc)(struct restricted_heap *heap, struct restricted_buffer *buf);
> +	void	(*memory_free)(struct restricted_heap *heap, struct restricted_buffer *buf);
> +
> +	int	(*memory_restrict)(struct restricted_heap *heap, struct restricted_buffer *buf);
> +	void	(*memory_unrestrict)(struct restricted_heap *heap, struct restricted_buffer *buf);
>
Is the prefix "memory_" superfluous here in these ops?

Also related to a comment on the prior patch. The name here is "heap" for
restricted_heap, but below you use rstrd_heap. It's the same struct, so I would
advise to use the same name to avoid confusion when reading the code. As
mentioned before, I think the name "rheap" would be a good choice.

>  };
>  
>  int restricted_heap_add(struct restricted_heap *rstrd_heap);
> -- 
> 2.25.1
> 

-- 
// Regards
Joakim