linux-kernel - Re: [PATCH v5 2/2] misc: fastrpc: Increase unsigned PD initmem size

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Message-ID: <2024072235-daydream-clunky-0272@gregkh>
Date: Mon, 22 Jul 2024 08:00:27 +0200
From: Greg KH <gregkh@...uxfoundation.org>
To: Ekansh Gupta <quic_ekangupt@...cinc.com>
Cc: srinivas.kandagatla@...aro.org, linux-arm-msm@...r.kernel.org,
	quic_bkumar@...cinc.com, linux-kernel@...r.kernel.org,
	quic_chennak@...cinc.com, dri-devel@...ts.freedesktop.org,
	arnd@...db.de, stable <stable@...nel.org>
Subject: Re: [PATCH v5 2/2] misc: fastrpc: Increase unsigned PD initmem size

On Mon, Jul 22, 2024 at 11:24:37AM +0530, Ekansh Gupta wrote:
> For unsigned PD offloading requirement, additional memory is required
> because of additional static heap initialization. Without this
> additional memory, PD initialization would fail. Increase the initmem
> size by 2MB for unsigned PD initmem buffer allocation. Any additional
> memory sent to DSP during PD init is used as the PD heap.
> 
> Fixes: 7f1f481263c3 ("misc: fastrpc: check before loading process to the DSP")
> Cc: stable <stable@...nel.org>
> Signed-off-by: Ekansh Gupta <quic_ekangupt@...cinc.com>
> ---
>  drivers/misc/fastrpc.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
> index a3a5b745936e..18668b020a87 100644
> --- a/drivers/misc/fastrpc.c
> +++ b/drivers/misc/fastrpc.c
> @@ -40,6 +40,7 @@
>  #define FASTRPC_CTXID_MASK (0xFF0)
>  #define INIT_FILELEN_MAX (2 * 1024 * 1024)
>  #define FASTRPC_INITLEN_MIN (3 * 1024 * 1024)
> +#define FASTRPC_STATIC_HEAP_LEN (2 * 1024 * 1024)
>  #define INIT_FILE_NAMELEN_MAX (128)
>  #define FASTRPC_DEVICE_NAME	"fastrpc"
>  
> @@ -1411,8 +1412,14 @@ static int fastrpc_init_create_process(struct fastrpc_user *fl,
>  			goto err;
>  	}
>  
> +	/* Allocate buffer in kernel for donating to remote process.
> +	 * Unsigned PD requires additional memory because of the

What is "PD"?

> +	 * additional static heap initialized within the process.
> +	 */

Why are you using networking comment style for a non-networking file?

>  	memlen = ALIGN(max(FASTRPC_INITLEN_MIN, (int)init.filelen * 4),
>  		       1024 * 1024);
> +	if (unsigned_module)
> +		memlen += FASTRPC_STATIC_HEAP_LEN;

I don't understand, why is "static heap length" being added for
something that is "unsigned"?  Why isn't this just "SIGNING FREE SPACE"
or something like that?

thanks,

greg "naming is hard" k-h