linux-kernel - Re: [PATCH v6 1/2] misc: fastrpc: Define a new initmem size for user PD

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Message-ID: <63c52fd2-9f31-418b-8c6c-4c91f7c69fd3@quicinc.com>
Date: Tue, 23 Jul 2024 10:04:57 +0530
From: Ekansh Gupta <quic_ekangupt@...cinc.com>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
CC: <srinivas.kandagatla@...aro.org>, <linux-arm-msm@...r.kernel.org>,
        <gregkh@...uxfoundation.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 v6 1/2] misc: fastrpc: Define a new initmem size for user
 PD



On 7/22/2024 2:02 PM, Dmitry Baryshkov wrote:
> On Mon, Jul 22, 2024 at 01:31:59PM GMT, Ekansh Gupta wrote:
>> For user PD initialization, initmem is allocated and sent to DSP for
>> initial memory requirements like shell loading. The size of this memory
>> is decided based on the shell size that is passed by the user space.
>> With the current implementation, a minimum of 2MB is always allocated
>> for initmem even if the size passed by user is less than that. For this
>> a MACRO is being used which is intended for shell size bound check.
>> This minimum size of 2MB is not recommended as the PD will have very
>> less memory for heap and will have to request HLOS again for memory.
>> Define a new macro for initmem minimum length of 3MB.
>>
>> Fixes: d73f71c7c6ee ("misc: fastrpc: Add support for create remote init process")
>> Cc: stable <stable@...nel.org>
>> Signed-off-by: Ekansh Gupta <quic_ekangupt@...cinc.com>
>> ---
>>  drivers/misc/fastrpc.c | 3 ++-
>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
>> index a7a2bcedb37e..a3a5b745936e 100644
>> --- a/drivers/misc/fastrpc.c
>> +++ b/drivers/misc/fastrpc.c
>> @@ -39,6 +39,7 @@
>>  #define FASTRPC_DSP_UTILITIES_HANDLE	2
>>  #define FASTRPC_CTXID_MASK (0xFF0)
>>  #define INIT_FILELEN_MAX (2 * 1024 * 1024)
>> +#define FASTRPC_INITLEN_MIN (3 * 1024 * 1024)
> So, what is the difference between INIT_FILELEN_MAX and
> FASTRPC_INITLEN_MIN?

INIT_FILELEN_MAX is the maximum shell size that can be passed by user.
FASTRPC_INITLEN_MIN is the minimum initmem length for PD.

>
>>  #define INIT_FILE_NAMELEN_MAX (128)
>>  #define FASTRPC_DEVICE_NAME	"fastrpc"
>>  
>> @@ -1410,7 +1411,7 @@ static int fastrpc_init_create_process(struct fastrpc_user *fl,
>>  			goto err;
>>  	}
>>  
>> -	memlen = ALIGN(max(INIT_FILELEN_MAX, (int)init.filelen * 4),
>> +	memlen = ALIGN(max(FASTRPC_INITLEN_MIN, (int)init.filelen * 4),
> BTW: why is the code multiplying filelen by 4? Nothing in the source
> code suggests that filelen is in u32 words, so I'd assume it's measured
> in bytes.

The passed filelen is actually the size of fastrpc shell. This size is not sufficient for the user
PD initialization. The 4x of filelen gives the approx. needed memory for signed PD initialization.
Yes, filelen is measured in bytes.

>
>>  		       1024 * 1024);
>>  	err = fastrpc_buf_alloc(fl, fl->sctx->dev, memlen,
>>  				&imem);
>> -- 
>> 2.34.1
>>