linux-kernel - Re: [PATCH v3 8/9] mailbox: mediatek: Add CMDQ secure mailbox driver

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Message-ID: <f3a8c0cbdcf5da0381eaee5e0595319cd1970dde.camel@mediatek.com>
Date: Thu, 28 Dec 2023 01:38:15 +0000
From: CK Hu (胡俊光) <ck.hu@...iatek.com>
To: "jassisinghbrar@...il.com" <jassisinghbrar@...il.com>,
	"matthias.bgg@...il.com" <matthias.bgg@...il.com>,
	Jason-JH Lin (林睿祥) <Jason-JH.Lin@...iatek.com>,
	"angelogioacchino.delregno@...labora.com"
	<angelogioacchino.delregno@...labora.com>, "robh+dt@...nel.org"
	<robh+dt@...nel.org>, "krzysztof.kozlowski+dt@...aro.org"
	<krzysztof.kozlowski+dt@...aro.org>, "chunkuang.hu@...nel.org"
	<chunkuang.hu@...nel.org>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mediatek@...ts.infradead.org" <linux-mediatek@...ts.infradead.org>,
	Singo Chang (張興國) <Singo.Chang@...iatek.com>,
	Johnson Wang (王聖鑫) <Johnson.Wang@...iatek.com>,
	"linux-media@...r.kernel.org" <linux-media@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Jason-ch Chen (陳建豪)
	<Jason-ch.Chen@...iatek.com>, Shawn Sung (宋孝謙)
	<Shawn.Sung@...iatek.com>, "mchehab@...nel.org" <mchehab@...nel.org>,
	Nancy Lin (林欣螢) <Nancy.Lin@...iatek.com>,
	"conor+dt@...nel.org" <conor+dt@...nel.org>,
	Project_Global_Chrome_Upstream_Group
	<Project_Global_Chrome_Upstream_Group@...iatek.com>,
	"linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v3 8/9] mailbox: mediatek: Add CMDQ secure mailbox driver

On Wed, 2023-12-27 at 07:25 +0000, Jason-JH Lin (林睿祥) wrote:
> Hi CK,
> 
> Thanks for the reviews.
> 
> On Tue, 2023-12-26 at 08:58 +0000, CK Hu (胡俊光) wrote:
> > Hi, Jason:
> > 
> > On Fri, 2023-12-22 at 12:52 +0800, Jason-JH.Lin wrote:
> > > To support secure video path feature, GCE have to read/write
> > > registgers
> > > in the secure world. GCE will enable the secure access permission
> > > to
> > > the
> > > HW who wants to access the secure content buffer.
> > > 
> > > Add CMDQ secure mailbox driver to make CMDQ client user is able
> > > to
> > > sending their HW settings to the secure world. So that GCE can
> > > execute
> > > all instructions to configure HW in the secure world.
> > > 
> > > Signed-off-by: Jason-JH.Lin <jason-jh.lin@...iatek.com>
> > > ---
> > 
> > [snip]
> > 
> > > +
> > > +static int cmdq_sec_fill_iwc_msg(struct cmdq_sec_context
> > > *context,
> > > +				 struct cmdq_sec_task *sec_task, u32
> > > thrd_idx)
> > > +{
> > > +	struct iwc_cmdq_message_t *iwc_msg = NULL;
> > > +	struct cmdq_sec_data *data = (struct cmdq_sec_data *)sec_task-
> > > > task.pkt->sec_data;
> > > 
> > > +	u32 size = 0, offset = 0, *instr;
> > > +
> > > +	iwc_msg = (struct iwc_cmdq_message_t *)context->iwc_msg;
> > > +
> > > +	if (sec_task->task.pkt->cmd_buf_size + 4 * CMDQ_INST_SIZE >
> > > CMDQ_TZ_CMD_BLOCK_SIZE) {
> > > +		pr_err("sec_task:%p size:%zu > %u",
> > > +		       sec_task, sec_task->task.pkt->cmd_buf_size,
> > > CMDQ_TZ_CMD_BLOCK_SIZE);
> > > +		return -EFAULT;
> > > +	}
> > > +
> > > +	if (thrd_idx == CMDQ_INVALID_THREAD) {
> > > +		iwc_msg->command.cmd_size = 0;
> > > +		iwc_msg->command.metadata.addr_list_length = 0;
> > > +		return -EINVAL;
> > > +	}
> > > +
> > > +	iwc_msg->command.thread = thrd_idx;
> > > +	iwc_msg->command.scenario = sec_task->scenario;
> > > +	iwc_msg->command.eng_flag = sec_task->engine_flag;
> > > +	size = sec_task->task.pkt->cmd_buf_size;
> > > +	memcpy(iwc_msg->command.va_base + offset, sec_task->task.pkt-
> > > > va_base, size);
> > 
> > I think it's not necessary to copy from normal command buffer to
> > normal
> > command buffer. Just
> > 
> > iwc_msg->command.va_base = sec_task->task.pkt->va_base;
> > 
> > You have a secure command buffer for secure gce to execute command.
> > If
> > you want to modify command buffer, copy from normal command buffer
> > to
> > secure command buffer, and modify the secure command buffer.
> > 
> > Regards,
> > CK
> > 
> > 
> 
> I think secure world won't recognize normal world's va, so we nee to
> copy to iwc_msg->command.va_base, which is a world share memory
> first.

Referring to cmdq_sec_allocate_wsm(), any kernel buffer could use
tee_shm_register_kernel_buf() to become share buffer between normal
world and secure world. In client driver, use tee_client_open_context()
to create tee context and register normal command buffer to be share
buffer. This would reduce the redundant memory copy.

Regards,
CK

> 
> Regards,
> Jason-JH.Lin