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

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Message-ID: <53b922b7-a87e-1447-0148-b96d51902bbf@linaro.org>
Date:   Mon, 9 Oct 2023 07:04:05 +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 03/10/2023 12:07, Ekansh Gupta wrote:
> 
> 
> On 10/2/2023 3:00 PM, Srinivas Kandagatla wrote:
>>
>>
>> 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?
>>
> The context specific rpra buffer is allocated as part of 
> fastrpc_get_args and there is a possibility that the DSP intends to 
> update fdlist for a call with 0 nscalars. In that scenario, the driver 
> needs to ensure that the rpra is allocated which will carry the fdlist. 
> The same can be extended to crc and dsp perf memory(to be added, patches 
> shared for missing features) for remote calls with 0 nscalars.
> 
Yes, we need this to setup remote args.

thanks
srini
> Thanks for taking your time to review the patches Srini, please let me 
> know if you have more queries.
> 
> -ekansh
>> --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) {