linux-kernel - Re: [PATCH V4 2/2] firmware: arm

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Message-ID: <20200304103954.GA25004@bogus>
Date:   Wed, 4 Mar 2020 10:40:05 +0000
From:   Sudeep Holla <sudeep.holla@....com>
To:     peng.fan@....com
Cc:     robh+dt@...nel.org, viresh.kumar@...aro.org, f.fainelli@...il.com,
        linux-imx@....com, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        Sudeep Holla <sudeep.holla@....com>
Subject: Re: [PATCH V4 2/2] firmware: arm_scmi: add smc/hvc transport

On Tue, Mar 03, 2020 at 10:06:59AM +0800, peng.fan@....com wrote:
> From: Peng Fan <peng.fan@....com>
>
> Take arm,smc-id as the 1st arg, leave the other args as zero for now.
> There is no Rx, only Tx because of smc/hvc not support Rx.
>
> Signed-off-by: Peng Fan <peng.fan@....com>

[...]

> +static int smc_send_message(struct scmi_chan_info *cinfo,
> +			    struct scmi_xfer *xfer)
> +{
> +	struct scmi_smc *scmi_info = cinfo->transport_info;
> +	struct arm_smccc_res res;
> +
> +	shmem_tx_prepare(scmi_info->shmem, xfer);

How do we protect another thread/process on another CPU going and
modifying the same shmem with another request ? We may need notion
of channel with associated shmem and it is protected with some lock.

--
Regards,
Sudeep