linux-kernel - Re: [PATCH v1 2/3] misc: fastrpc: Free DMA handles for RPC calls with no arguments

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Date:   Mon, 2 Oct 2023 10:30:13 +0100
From:   Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To:     Ekansh Gupta <quic_ekangupt@...cinc.com>,
        linux-arm-msm@...r.kernel.org
Cc:     ekangupt@....qualcomm.com, gregkh@...uxfoundation.org,
        linux-kernel@...r.kernel.org, fastrpc.upstream@....qualcomm.com,
        stable <stable@...nel.org>
Subject: Re: [PATCH v1 2/3] misc: fastrpc: Free DMA handles for RPC calls with
 no arguments



On 29/09/2023 08:42, Ekansh Gupta wrote:
> The FDs for DMA handles to be freed is updated in fdlist by DSP over
> a remote call. This holds true even for remote calls with no
> arguments. To handle this, get_args and put_args are needed to
> be called for remote calls with no arguments also as fdlist
> is allocated in get_args and FDs updated in fdlist is freed
> in put_args.
> 
> Fixes: 8f6c1d8c4f0c ("misc: fastrpc: Add fdlist implementation")
> Cc: stable <stable@...nel.org>
> Signed-off-by: Ekansh Gupta <quic_ekangupt@...cinc.com>
> ---
>   drivers/misc/fastrpc.c | 23 ++++++++++-------------
>   1 file changed, 10 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
> index fb92197..a52701c 100644
> --- a/drivers/misc/fastrpc.c
> +++ b/drivers/misc/fastrpc.c
> @@ -1091,6 +1091,7 @@ static int fastrpc_put_args(struct fastrpc_invoke_ctx *ctx,
>   		}
>   	}
>   
> +	/* Clean up fdlist which is updated by DSP */
>   	for (i = 0; i < FASTRPC_MAX_FDLIST; i++) {
>   		if (!fdlist[i])
>   			break;
> @@ -1157,11 +1158,9 @@ static int fastrpc_internal_invoke(struct fastrpc_user *fl,  u32 kernel,
>   	if (IS_ERR(ctx))
>   		return PTR_ERR(ctx);
>   
<---
> -	if (ctx->nscalars) {
> -		err = fastrpc_get_args(kernel, ctx);
> -		if (err)
> -			goto bail;
> -	}
> +	err = fastrpc_get_args(kernel, ctx);
> +	if (err)
> +		goto bail;
-->
I dont see any point of the above change as fastrpc_internal_invoke will 
be called from kernel with nscalars always set.

do you see a path that does not set this?

--srini
>   
>   	/* make sure that all CPU memory writes are seen by DSP */
>   	dma_wmb();
> @@ -1185,14 +1184,12 @@ static int fastrpc_internal_invoke(struct fastrpc_user *fl,  u32 kernel,
>   	if (err)
>   		goto bail;
>   
> -	if (ctx->nscalars) {
> -		/* make sure that all memory writes by DSP are seen by CPU */
> -		dma_rmb();
> -		/* populate all the output buffers with results */
> -		err = fastrpc_put_args(ctx, kernel);
> -		if (err)
> -			goto bail;
> -	}
> +	/* make sure that all memory writes by DSP are seen by CPU */
> +	dma_rmb();
> +	/* populate all the output buffers with results */
> +	err = fastrpc_put_args(ctx, kernel);
> +	if (err)
> +		goto bail;
>   
>   bail:
>   	if (err != -ERESTARTSYS && err != -ETIMEDOUT) {