Re: [PATCH v2] drm/imagination: simplify pvr_fw_trace_seq_data

[Alexandru Dadu]

Hi Rosen,

On Mon, 2026-10-05 at 12:41 -0700, Rosen Penev wrote:
> The trace buffer copy always has
> ROGUE_FW_TRACE_BUF_DEFAULT_SIZE_IN_DWORDS
> entries, so embed it in struct pvr_fw_trace_seq_data as a fixed-size
> array instead of allocating it separately. This removes one
> allocation
> and its error handling, and lets FORTIFY_SOURCE and UBSAN_BOUNDS see
> the
> real size of the buffer.
> 
> At about 48KB, the struct needs an order-4 page allocation, which can
> fail under memory fragmentation. Allocate it with kvzalloc_obj() so
> it
> falls back to vmalloc in that case, and free it with kvfree().
> 
> Assisted-by: LLM
> Signed-off-by: Rosen Penev <rosenp@xxxxxxxxx>

Reviewed-by: Alexandru Dadu <alexandru.dadu@xxxxxxxxxx>

Thanks,
Alexandru Dadu
> ---
>  v2: use kvzalloc_obj()
>  drivers/gpu/drm/imagination/pvr_fw_trace.c | 25 ++++++--------------
> --
>  1 file changed, 7 insertions(+), 18 deletions(-)
> 
> diff --git a/drivers/gpu/drm/imagination/pvr_fw_trace.c
> b/drivers/gpu/drm/imagination/pvr_fw_trace.c
> index 6fe478f64f02..27bbc62114b1 100644
> --- a/drivers/gpu/drm/imagination/pvr_fw_trace.c
> +++ b/drivers/gpu/drm/imagination/pvr_fw_trace.c
> @@ -240,9 +240,6 @@ update_logtype(struct pvr_device *pvr_dev, u32
> group_mask)
>  }
>  
>  struct pvr_fw_trace_seq_data {
> -	/** @buffer: Pointer to copy of trace data. */
> -	u32 *buffer;
> -
>  	/** @start_offset: Starting offset in trace data, as
> reported by FW. */
>  	u32 start_offset;
>  
> @@ -251,6 +248,9 @@ struct pvr_fw_trace_seq_data {
>  
>  	/** @assert_buf: Trace assert buffer, as reported by FW. */
>  	struct rogue_fwif_file_info_buf assert_buf;
> +
> +	/** @buffer: Copy of trace data. */
> +	u32 buffer[ROGUE_FW_TRACE_BUF_DEFAULT_SIZE_IN_DWORDS];
>  };
>  
>  static u32 find_sfid(u32 id)
> @@ -454,17 +454,10 @@ static int fw_trace_open(struct inode *inode,
> struct file *file)
>  	struct pvr_fw_trace_seq_data *trace_seq_data;
>  	int err;
>  
> -	trace_seq_data = kzalloc_obj(*trace_seq_data);
> +	trace_seq_data = kvzalloc_obj(*trace_seq_data);
>  	if (!trace_seq_data)
>  		return -ENOMEM;
>  
> -	trace_seq_data->buffer =
> kcalloc(ROGUE_FW_TRACE_BUF_DEFAULT_SIZE_IN_DWORDS,
> -					 sizeof(*trace_seq_data-
> >buffer), GFP_KERNEL);
> -	if (!trace_seq_data->buffer) {
> -		err = -ENOMEM;
> -		goto err_free_data;
> -	}
> -
>  	/*
>  	 * Take a local copy of the trace buffer, as firmware may
> still be
>  	 * writing to it. This will exist as long as this file is
> open.
> @@ -477,17 +470,14 @@ static int fw_trace_open(struct inode *inode,
> struct file *file)
>  
>  	err = seq_open(file, &pvr_fw_trace_seq_ops);
>  	if (err)
> -		goto err_free_buffer;
> +		goto err_free_data;
>  
>  	((struct seq_file *)file->private_data)->private =
> trace_seq_data;
>  
>  	return 0;
>  
> -err_free_buffer:
> -	kfree(trace_seq_data->buffer);
> -
>  err_free_data:
> -	kfree(trace_seq_data);
> +	kvfree(trace_seq_data);
>  
>  	return err;
>  }
> @@ -498,8 +488,7 @@ static int fw_trace_release(struct inode *inode,
> struct file *file)
>  		((struct seq_file *)file->private_data)->private;
>  
>  	seq_release(inode, file);
> -	kfree(trace_seq_data->buffer);
> -	kfree(trace_seq_data);
> +	kvfree(trace_seq_data);
>  
>  	return 0;
>  }