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Date:   Fri, 31 Mar 2023 09:25:29 -0500
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From:   Alex Elder <elder@linaro.org>
Subject: Re: [PATCH v11 08/26] gunyah: rsc_mgr: Add resource manager RPC core
To:     Elliot Berman <quic_eberman@quicinc.com>,
        Srinivas Kandagatla <srinivas.kandagatla@linaro.org>,
        Prakruthi Deepak Heragu <quic_pheragu@quicinc.com>
Cc:     Murali Nalajala <quic_mnalajal@quicinc.com>,
        Trilok Soni <quic_tsoni@quicinc.com>,
        Srivatsa Vaddagiri <quic_svaddagi@quicinc.com>,
        Carl van Schaik <quic_cvanscha@quicinc.com>,
        Dmitry Baryshkov <dmitry.baryshkov@linaro.org>,
        Bjorn Andersson <andersson@kernel.org>,
        Konrad Dybcio <konrad.dybcio@linaro.org>,
        Arnd Bergmann <arnd@arndb.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Jonathan Corbet <corbet@lwn.net>,
        Bagas Sanjaya <bagasdotme@gmail.com>,
        Will Deacon <will@kernel.org>, Andy Gross <agross@kernel.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Jassi Brar <jassisinghbrar@gmail.com>,
        linux-arm-msm@vger.kernel.org, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org
References: <20230304010632.2127470-1-quic_eberman@quicinc.com>
 <20230304010632.2127470-9-quic_eberman@quicinc.com>
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On 3/3/23 7:06 PM, Elliot Berman wrote:
> The resource manager is a special virtual machine which is always
> running on a Gunyah system. It provides APIs for creating and destroying
> VMs, secure memory management, sharing/lending of memory between VMs,
> and setup of inter-VM communication. Calls to the resource manager are
> made via message queues.
> 
> This patch implements the basic probing and RPC mechanism to make those
> API calls. Request/response calls can be made with gh_rm_call.
> Drivers can also register to notifications pushed by RM via
> gh_rm_register_notifier
> 
> Specific API calls that resource manager supports will be implemented in
> subsequent patches.

Mostly very simple issues noted here.	-Alex

> Signed-off-by: Elliot Berman <quic_eberman@quicinc.com>
> ---
>   drivers/virt/gunyah/Makefile   |   3 +
>   drivers/virt/gunyah/rsc_mgr.c  | 688 +++++++++++++++++++++++++++++++++
>   drivers/virt/gunyah/rsc_mgr.h  |  16 +
>   include/linux/gunyah_rsc_mgr.h |  21 +
>   4 files changed, 728 insertions(+)
>   create mode 100644 drivers/virt/gunyah/rsc_mgr.c
>   create mode 100644 drivers/virt/gunyah/rsc_mgr.h
>   create mode 100644 include/linux/gunyah_rsc_mgr.h
> 
> diff --git a/drivers/virt/gunyah/Makefile b/drivers/virt/gunyah/Makefile
> index 34f32110faf9..cc864ff5abbb 100644
> --- a/drivers/virt/gunyah/Makefile
> +++ b/drivers/virt/gunyah/Makefile
> @@ -1,3 +1,6 @@
>   # SPDX-License-Identifier: GPL-2.0
>   
>   obj-$(CONFIG_GUNYAH) += gunyah.o
> +
> +gunyah_rsc_mgr-y += rsc_mgr.o
> +obj-$(CONFIG_GUNYAH) += gunyah_rsc_mgr.o
> diff --git a/drivers/virt/gunyah/rsc_mgr.c b/drivers/virt/gunyah/rsc_mgr.c
> new file mode 100644
> index 000000000000..67813c9a52db
> --- /dev/null
> +++ b/drivers/virt/gunyah/rsc_mgr.c
> @@ -0,0 +1,688 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (c) 2022-2023 Qualcomm Innovation Center, Inc. All rights reserved.
> + */
> +

. . .

> +static void gh_rm_try_complete_connection(struct gh_rm *rm)
> +{
> +	struct gh_rm_connection *connection = rm->active_rx_connection;
> +
> +	if (!connection || connection->fragments_received != connection->num_fragments)
> +		return;
> +
> +	switch (connection->type) {
> +	case RM_RPC_TYPE_REPLY:
> +		complete(&connection->reply.seq_done);
> +		break;
> +	case RM_RPC_TYPE_NOTIF:
> +		schedule_work(&connection->notification.work);
> +		break;
> +	default:
> +		dev_err_ratelimited(rm->dev, "Invalid message type (%d) received\n",

s/%d/%u/

> +					connection->type);
> +		gh_rm_abort_connection(rm);
> +		break;
> +	}
> +
> +	rm->active_rx_connection = NULL;
> +}
> +
> +static void gh_rm_msgq_rx_data(struct mbox_client *cl, void *mssg)
> +{
> +	struct gh_rm *rm = container_of(cl, struct gh_rm, msgq_client);
> +	struct gh_msgq_rx_data *rx_data = mssg;
> +	size_t msg_size = rx_data->length;
> +	void *msg = rx_data->data;
> +	struct gh_rm_rpc_hdr *hdr;
> +
> +	if (msg_size < sizeof(*hdr) || msg_size > GH_MSGQ_MAX_MSG_SIZE)
> +		return;
> +
> +	hdr = msg;
> +	if (hdr->api != RM_RPC_API) {
> +		dev_err(rm->dev, "Unknown RM RPC API version: %x\n", hdr->api);
> +		return;
> +	}
> +
> +	switch (FIELD_GET(RM_RPC_TYPE_MASK, hdr->type)) {
> +	case RM_RPC_TYPE_NOTIF:
> +		gh_rm_process_notif(rm, msg, msg_size);
> +		break;
> +	case RM_RPC_TYPE_REPLY:
> +		gh_rm_process_rply(rm, msg, msg_size);
> +		break;
> +	case RM_RPC_TYPE_CONTINUATION:
> +		gh_rm_process_cont(rm, rm->active_rx_connection, msg, msg_size);
> +		break;
> +	default:
> +		dev_err(rm->dev, "Invalid message type (%lu) received\n",
> +			FIELD_GET(RM_RPC_TYPE_MASK, hdr->type));
> +		return;
> +	}
> +
> +	gh_rm_try_complete_connection(rm);
> +}
> +
> +static void gh_rm_msgq_tx_done(struct mbox_client *cl, void *mssg, int r)
> +{
> +	struct gh_rm *rm = container_of(cl, struct gh_rm, msgq_client);
> +
> +	kmem_cache_free(rm->cache, mssg);
> +	rm->last_tx_ret = r;
> +}
> +
> +static int gh_rm_send_request(struct gh_rm *rm, u32 message_id,
> +			      const void *req_buff, size_t req_buf_size,
> +			      struct gh_rm_connection *connection)
> +{
> +	size_t buf_size_remaining = req_buf_size;
> +	const void *req_buf_curr = req_buff;
> +	struct gh_msgq_tx_data *msg;
> +	struct gh_rm_rpc_hdr *hdr, hdr_template;
> +	u32 cont_fragments = 0;
> +	size_t payload_size;
> +	void *payload;
> +	int ret;
> +
> +	if (req_buf_size > GH_RM_MAX_NUM_FRAGMENTS * GH_RM_MAX_MSG_SIZE) {
> +		dev_warn(rm->dev, "Limit exceeded for the number of fragments: %u\n",
> +			cont_fragments);

You are printing the value of cont_fragments here when it's just zero.

> +		dump_stack();
> +		return -E2BIG;
> +	}
> +

Move the computation of cont_fragments prior to the block above.
You could use a ?: statement to assign it.

> +	if (req_buf_size)
> +		cont_fragments = (req_buf_size - 1) / GH_RM_MAX_MSG_SIZE;
> +
> +	hdr_template.api = RM_RPC_API;
> +	hdr_template.type = FIELD_PREP(RM_RPC_TYPE_MASK, RM_RPC_TYPE_REQUEST) |
> +			FIELD_PREP(RM_RPC_FRAGMENTS_MASK, cont_fragments);

The line above should be indented further.

> +	hdr_template.seq = cpu_to_le16(connection->reply.seq);
> +	hdr_template.msg_id = cpu_to_le32(message_id);
> +
> +	ret = mutex_lock_interruptible(&rm->send_lock);
> +	if (ret)
> +		return ret;
> +
> +	/* Consider also the 'request' packet for the loop count */

I don't think the comment above is helpful.

> +	do {
> +		msg = kmem_cache_zalloc(rm->cache, GFP_KERNEL);
> +		if (!msg) {
> +			ret = -ENOMEM;
> +			goto out;
> +		}
> +
> +		/* Fill header */
> +		hdr = (struct gh_rm_rpc_hdr *)msg->data;

I personally would prefer &msg->data[0] in this case.

> +		*hdr = hdr_template;
> +
> +		/* Copy payload */
> +		payload = hdr + 1;

I think I might have suggested using "hdr + 1" here.

Elsewhere you use something like:
	payload = (char *)hdr + sizeof(hdr);
or something similar.  I suggest you choose one approach and use
it consistently througout the driver.  Either is fine, but I
have a slight preference for the "hdr + 1" way.

> +		payload_size = min(buf_size_remaining, GH_RM_MAX_MSG_SIZE);
> +		memcpy(payload, req_buf_curr, payload_size);
> +		req_buf_curr += payload_size;
> +		buf_size_remaining -= payload_size;
> +
> +		/* Force the last fragment to immediately alert the receiver */
> +		msg->push = !buf_size_remaining;
> +		msg->length = sizeof(*hdr) + payload_size;
> +
> +		ret = mbox_send_message(gh_msgq_chan(&rm->msgq), msg);
> +		if (ret < 0) {
> +			kmem_cache_free(rm->cache, msg);
> +			break;
> +		}
> +
> +		if (rm->last_tx_ret) {
> +			ret = rm->last_tx_ret;
> +			break;
> +		}
> +
> +		hdr_template.type = FIELD_PREP(RM_RPC_TYPE_MASK, RM_RPC_TYPE_CONTINUATION) |
> +					FIELD_PREP(RM_RPC_FRAGMENTS_MASK, cont_fragments);
> +	} while (buf_size_remaining);
> +
> +out:
> +	mutex_unlock(&rm->send_lock);
> +	return ret < 0 ? ret : 0;
> +}
> +
> +/**
> + * gh_rm_call: Achieve request-response type communication with RPC
> + * @rm: Pointer to Gunyah resource manager internal data
> + * @message_id: The RM RPC message-id
> + * @req_buff: Request buffer that contains the payload
> + * @req_buf_size: Total size of the payload
> + * @resp_buf: Pointer to a response buffer
> + * @resp_buf_size: Size of the response buffer
> + *
> + * Make a request to the RM-VM and wait for reply back. For a successful

I think you could just say "to the RM and wait"...

Overall I suggest using "RM" or "RM VM" consistently when you talk
about the Resource Manager.  This is the only place I see "RM-VM".

> + * response, the function returns the payload. The size of the payload is set in
> + * resp_buf_size. The resp_buf should be freed by the caller when 0 is returned

s/should/must/

> + * and resp_buf_size != 0.
> + *
> + * req_buff should be not NULL for req_buf_size >0. If req_buf_size == 0,
> + * req_buff *can* be NULL and no additional payload is sent.

I'd say use "buf" or "buff" but not both in your naming
convention.

> + *
> + * Context: Process context. Will sleep waiting for reply.
> + * Return: 0 on success. <0 if error.
> + */
> +int gh_rm_call(struct gh_rm *rm, u32 message_id, void *req_buff, size_t req_buf_size,
> +		void **resp_buf, size_t *resp_buf_size)

I suspect you could define the request buffer as a pointer to const;
can you?

> +{
> +	struct gh_rm_connection *connection;
> +	u32 seq_id;
> +	int ret;
> +
> +	/* message_id 0 is reserved. req_buf_size implies req_buf is not NULL */
> +	if (!message_id || (!req_buff && req_buf_size) || !rm)

If you're going to check for a null RM pointer, I'd check it first.

> +		return -EINVAL;
> +
> +
> +	connection = kzalloc(sizeof(*connection), GFP_KERNEL);
> +	if (!connection)
> +		return -ENOMEM;
> +
> +	connection->type = RM_RPC_TYPE_REPLY;
> +	connection->msg_id = cpu_to_le32(message_id);
> +
> +	init_completion(&connection->reply.seq_done);

. . .

> diff --git a/include/linux/gunyah_rsc_mgr.h b/include/linux/gunyah_rsc_mgr.h
> new file mode 100644
> index 000000000000..deca9b3da541
> --- /dev/null
> +++ b/include/linux/gunyah_rsc_mgr.h
> @@ -0,0 +1,21 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Copyright (c) 2022-2023 Qualcomm Innovation Center, Inc. All rights reserved.
> + */
> +
> +#ifndef _GUNYAH_RSC_MGR_H
> +#define _GUNYAH_RSC_MGR_H
> +
> +#include <linux/list.h>
> +#include <linux/notifier.h>
> +#include <linux/gunyah.h>
> +
> +#define GH_VMID_INVAL	U16_MAX

Add a tab before U16_MAX; it will line up more nicely
when you define GH_MEM_HANDLE_INVAL later.

> +
> +struct gh_rm;
> +int gh_rm_notifier_register(struct gh_rm *rm, struct notifier_block *nb);
> +int gh_rm_notifier_unregister(struct gh_rm *rm, struct notifier_block *nb);
> +struct device *gh_rm_get(struct gh_rm *rm);
> +void gh_rm_put(struct gh_rm *rm);
> +
> +#endif