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

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Date:   Tue, 26 Sep 2023 11:27:51 +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
Subject: Re: [PATCH v1] misc: fastrpc: Free DMA handles for RPC calls with no
 arguments

Thanks Ekansh for this patch.

few comments below

On 31/08/2023 07:23, Ekansh Gupta wrote:
> The FDs for DMA handles to be freed is updated in fdlist by DSP over

So the dsp is updating the fd list after invoke?


> 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.
> 
> Signed-off-by: Ekansh Gupta <quic_ekangupt@...cinc.com>
> ---
>   drivers/misc/fastrpc.c | 22 +++++++++-------------
>   1 file changed, 9 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
> index 9666d28..e6df66e 100644
> --- a/drivers/misc/fastrpc.c
> +++ b/drivers/misc/fastrpc.c
> @@ -1153,11 +1153,9 @@ static int fastrpc_internal_invoke(struct fastrpc_user *fl,  u32 kernel,
>   	if (IS_ERR(ctx))
>   		return PTR_ERR(ctx);
>   
> -	if (ctx->nscalars) {

Why do we need to remove this check?
fastrpc_internal_invoke will have nscalars set before calling. and we 
are not dealing with fdlist in fastrpc_get_args(), so am not sure what 
this change is helping with.


> -		err = fastrpc_get_args(kernel, ctx);
> -		if (err)
> -			goto bail;
> -	}
> +	err = fastrpc_get_args(kernel, ctx);
> +	if (err)
> +		goto bail;
>   
>   	/* make sure that all CPU memory writes are seen by DSP */
>   	dma_wmb();
> @@ -1181,14 +1179,12 @@ 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 */

A comment about fdlist here would be really useful

> +	err = fastrpc_put_args(ctx, kernel);
> +	if (err)
> +		goto bail;
>   
>   bail:
>   	if (err != -ERESTARTSYS && err != -ETIMEDOUT) {