Re: [PATCH v5 09/13] mailbox: Add Gunyah message queue mailbox

[Dmitry Baryshkov]

On 11/10/2022 03:08, Elliot Berman wrote:
> Gunyah message queues are a unidirectional inter-VM pipe for messages up
> to 1024 bytes. This driver supports pairing a receiver message queue and
> a transmitter message queue to expose a single mailbox channel.
>
> Signed-off-by: Elliot Berman <quic_eberman@xxxxxxxxxxx>
> ---
>   MAINTAINERS                   |   2 +
>   drivers/mailbox/Kconfig       |  10 ++
>   drivers/mailbox/Makefile      |   2 +
>   drivers/mailbox/gunyah-msgq.c | 254 ++++++++++++++++++++++++++++++++++
>   drivers/virt/gunyah/Kconfig   |   2 +
>   include/linux/gunyah.h        |  67 +++++++++
>   6 files changed, 337 insertions(+)
>   create mode 100644 drivers/mailbox/gunyah-msgq.c
>   create mode 100644 include/linux/gunyah.h
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index c5458aeec023..599804836d05 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -8888,8 +8888,10 @@ F:	Documentation/ABI/testing/sysfs-hypervisor-gunyah
>   F:	Documentation/devicetree/bindings/firmware/gunyah-hypervisor.yaml
>   F:	Documentation/virt/gunyah/
>   F:	arch/arm64/gunyah/
> +F:	drivers/mailbox/gunyah-msgq.c
>   F:	drivers/virt/gunyah/
>   F:	include/asm-generic/gunyah.h
> +F:	include/linux/gunyah.h
>   
>   HABANALABS PCI DRIVER
>   M:	Oded Gabbay <ogabbay@xxxxxxxxxx>
> diff --git a/drivers/mailbox/Kconfig b/drivers/mailbox/Kconfig
> index 05d6fae800e3..baf9451c5f04 100644
> --- a/drivers/mailbox/Kconfig
> +++ b/drivers/mailbox/Kconfig
> @@ -41,6 +41,16 @@ config IMX_MBOX
>   	help
>   	  Mailbox implementation for i.MX Messaging Unit (MU).
>   
> +config GUNYAH_MESSAGE_QUEUES
> +	tristate "Gunyah Message Queue Mailbox"
> +	depends on GUNYAH
> +	help
> +	  Mailbox implementation for Gunyah Message Queues. Gunyah message queues
> +	  are an IPC mechanism to pass short messages between virtual machines
> +	  running under the Gunyah hypervisor.
> +
> +	  Say Y here if you run Linux as a Gunyah virtual machine.
> +
>   config PLATFORM_MHU
>   	tristate "Platform MHU Mailbox"
>   	depends on OF
> diff --git a/drivers/mailbox/Makefile b/drivers/mailbox/Makefile
> index fc9376117111..5f929bb55e9a 100644
> --- a/drivers/mailbox/Makefile
> +++ b/drivers/mailbox/Makefile
> @@ -55,6 +55,8 @@ obj-$(CONFIG_MTK_CMDQ_MBOX)	+= mtk-cmdq-mailbox.o
>   
>   obj-$(CONFIG_ZYNQMP_IPI_MBOX)	+= zynqmp-ipi-mailbox.o
>   
> +obj-$(CONFIG_GUNYAH)		+= gunyah-msgq.o
> +
>   obj-$(CONFIG_SUN6I_MSGBOX)	+= sun6i-msgbox.o
>   
>   obj-$(CONFIG_SPRD_MBOX)		+= sprd-mailbox.o
> diff --git a/drivers/mailbox/gunyah-msgq.c b/drivers/mailbox/gunyah-msgq.c
> new file mode 100644
> index 000000000000..f0cd96920c64
> --- /dev/null
> +++ b/drivers/mailbox/gunyah-msgq.c
> @@ -0,0 +1,254 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (c) 2022 Qualcomm Innovation Center, Inc. All rights reserved.
> + */
> +
> +#include <linux/mailbox_controller.h>
> +#include <linux/module.h>
> +#include <linux/interrupt.h>
> +#include <linux/gunyah.h>
> +#include <linux/printk.h>
> +#include <linux/init.h>
> +#include <linux/slab.h>
> +#include <linux/wait.h>
> +
> +#define mbox_chan_to_msgq(chan) (container_of(chan->mbox, struct gunyah_msgq, mbox))
> +
> +static inline bool gh_msgq_has_tx(struct gunyah_msgq *msgq)
> +{
> +	return msgq->tx_ghrsc.type == GUNYAH_RESOURCE_TYPE_MSGQ_TX;
> +}
> +
> +static inline bool gh_msgq_has_rx(struct gunyah_msgq *msgq)
> +{
> +	return msgq->rx_ghrsc.type == GUNYAH_RESOURCE_TYPE_MSGQ_RX;
> +}
> +
> +static ssize_t __gh_msgq_recv(struct gunyah_msgq *msgq, void *buff, size_t size, bool *ready)
> +{
> +	unsigned long gh_err;
> +	size_t recv_size;
> +	ssize_t ret;
> +
> +	gh_err = gh_hypercall_msgq_recv(msgq->rx_ghrsc.capid, (uintptr_t)buff, size,
> +					&recv_size, ready);
> +	switch (gh_err) {
> +	case GH_ERROR_OK:
> +		ret = recv_size;
> +		break;
> +	case GH_ERROR_MSGQUEUE_EMPTY:
> +		ret = -EAGAIN;
> +		*ready = false;
> +		break;
> +	default:
> +		ret = gh_remap_error(gh_err);
> +		break;
> +	}
> +
> +	return ret;
> +}
> +
> +static irqreturn_t gh_msgq_rx_irq_handler(int irq, void *data)
> +{
> +	struct gunyah_msgq *msgq = data;
> +	struct gunyah_msgq_rx_data rx_data;
> +	ssize_t ret;
> +	bool more;
> +
> +	do {
> +		ret = __gh_msgq_recv(msgq, &rx_data.data, sizeof(rx_data.data), &more);

Inline the call please.

> +
> +		if (ret >= 0) {
> +			rx_data.length = ret;
> +			mbox_chan_received_data(gunyah_msgq_chan(msgq), &rx_data);
> +		} else if (ret != -EAGAIN)
> +			pr_warn("Failed to receive data from msgq for %s: %ld\n",
> +				msgq->mbox.dev ? dev_name(msgq->mbox.dev) : "", ret);
> +	} while (ret >= 0);
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static irqreturn_t gh_msgq_tx_irq_handler(int irq, void *data)
> +{
> +	struct gunyah_msgq *msgq = data;
> +
> +	mbox_chan_txdone(gunyah_msgq_chan(msgq), 0);
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static void gh_msgq_txdone_tasklet(unsigned long data)
> +{
> +	struct gunyah_msgq *msgq = (struct gunyah_msgq *)data;
> +
> +	mbox_chan_txdone(gunyah_msgq_chan(msgq), msgq->last_status);

I don't quite get this. Why do you need both an IRQ and a tasklet?

> +}
> +
> +static int __gh_msgq_send(struct gunyah_msgq *msgq, void *buff, size_t size, u64 tx_flags)
> +{
> +	unsigned long gh_err;
> +	ssize_t ret;
> +	bool ready;
> +
> +	gh_err = gh_hypercall_msgq_send(msgq->tx_ghrsc.capid, size, (uintptr_t)buff, tx_flags,
> +					&ready);
> +	switch (gh_err) {
> +	case GH_ERROR_OK:
> +		ret = !ready;
> +		break;
> +	case GH_ERROR_MSGQUEUE_FULL:
> +		ret = -EAGAIN;
> +		break;
> +	default:
> +		/* Not sure how to propagate these out to client. If we get here, nobody is going
> +		 * to trigger a retry
> +		 */
> +		ret = gh_remap_error(gh_err);
> +		break;
> +	}
> +
> +	return ret;
> +}
> +
> +static int gh_msgq_send_data(struct mbox_chan *chan, void *data)
> +{
> +	struct gunyah_msgq *msgq = mbox_chan_to_msgq(chan);
> +	struct gunyah_msgq_tx_data *msgq_data = data;
> +	u64 tx_flags = 0;
> +	int ret;
> +
> +	if (msgq_data->push)
> +		tx_flags |= GH_HYPERCALL_MSGQ_TX_FLAGS_PUSH;
> +
> +	ret = __gh_msgq_send(msgq, msgq_data->data, msgq_data->length, tx_flags);

Inline the call.

> +
> +	/**
> +	 * EAGAIN: message didn't send.
> +	 * ret = 1: message sent, but now the message queue is full and we can't send any more msgs.
> +	 * Either way, don't report that this message is done.
> +	 */
> +	if (ret == -EAGAIN || ret == 1)
> +		return ret;

'1' doesn't seem to be a valid return code for _send_data.

Also it would be logical to return any error here, not just -EAGAIN.

> +
> +	/**
> +	 * Mailbox framework requires that tx done happens asynchronously to sending the message
> +	 * IOW, a notification that the message was sent happens after sending the message.
> +	 * To work around this, defer the txdone to a tasklet.
> +	 */
> +	msgq->last_status = ret;
> +	tasklet_schedule(&msgq->txdone_tasklet);
> +
> +	return 0;
> +}
> +
> +struct mbox_chan_ops gunyah_msgq_ops = {
> +	.send_data = gh_msgq_send_data,
> +};
> +
> +/**
> + * gunyah_msgq_init() - Initialize a Gunyah message queue with an mbox_client
> + * @parent: optional, device parent used for the mailbox controller
> + * @msgq: Pointer to the gunyah_msgq to initialize
> + * @cl: A mailbox client to bind to the mailbox channel that the message queue creates
> + * @tx_ghrsc: optional, the transmission side of the message queue
> + * @rx_ghrsc: optional, the receiving side of the message queue
> + *
> + * At least one of tx_ghrsc and rx_ghrsc should be not NULL. Most message queue use cases come with
> + * a pair of message queues to facilitiate bidirectional communication. When tx_ghrsc is set,
> + * the client can send messages with mbox_send_message(gunyah_msgq_chan(msgq), msg). When rx_ghrsc
> + * is set, the mbox_client should register an .rx_callback() and the message queue driver will
> + * push all available messages upon receiving the RX ready interrupt. The messages should be
> + * consumed or copied by the client right away as the gunyah_msgq_rx_data will be replaced/destroyed
> + * after the callback.
> + *
> + * Returns - 0 on success, negative otherwise
> + */
> +int gunyah_msgq_init(struct device *parent, struct gunyah_msgq *msgq, struct mbox_client *cl,
> +		     struct gunyah_resource *tx_ghrsc, struct gunyah_resource *rx_ghrsc)

Are the message queues allocated/created dynamically or statically? If 
the later is true, please use devm_request(_threaded)_irq and devm_kzalloc.

> +{
> +	int ret;
> +
> +	/* Must have at least a tx_ghrsc or rx_ghrsc and that they are the right device types */
> +	if ((!tx_ghrsc && !rx_ghrsc) ||
> +	    (tx_ghrsc && tx_ghrsc->type != GUNYAH_RESOURCE_TYPE_MSGQ_TX) ||
> +	    (rx_ghrsc && rx_ghrsc->type != GUNYAH_RESOURCE_TYPE_MSGQ_RX))
> +		return -EINVAL;
> +
> +	msgq->tx_ghrsc = *tx_ghrsc;
> +	msgq->rx_ghrsc = *rx_ghrsc;

Why? You can just turn msg->tx_ghrsc/rx_ghrsc into pointers and just 
assign them here.

> +
> +	msgq->mbox.dev = parent;
> +	msgq->mbox.ops = &gunyah_msgq_ops;
> +	msgq->mbox.chans = kcalloc(1, sizeof(*msgq->mbox.chans), GFP_KERNEL);

kzalloc?

> +	msgq->mbox.num_chans = 1;
> +	msgq->mbox.txdone_irq = true;
> +
> +	if (gh_msgq_has_tx(msgq)) {
> +		ret = request_irq(msgq->tx_ghrsc.irq, gh_msgq_tx_irq_handler, 0, "gh_msgq_tx",
> +				msgq);
> +		if (ret)
> +			goto err_chans;
> +	}
> +
> +	if (gh_msgq_has_rx(msgq)) {
> +		ret = request_threaded_irq(msgq->rx_ghrsc.irq, NULL, gh_msgq_rx_irq_handler,
> +						IRQF_ONESHOT, "gh_msgq_rx", msgq);
> +		if (ret)
> +			goto err_tx_irq;
> +	}
> +
> +	tasklet_init(&msgq->txdone_tasklet, gh_msgq_txdone_tasklet, (unsigned long)msgq);
> +
> +	ret = mbox_controller_register(&msgq->mbox);
> +	if (ret)
> +		goto err_rx_irq;
> +
> +	ret = mbox_bind_client(gunyah_msgq_chan(msgq), cl);
> +	if (ret)
> +		goto err_mbox;
> +
> +	return 0;
> +err_mbox:
> +	mbox_controller_unregister(&msgq->mbox);
> +err_rx_irq:
> +	if (gh_msgq_has_rx(msgq))
> +		free_irq(msgq->rx_ghrsc.irq, msgq);
> +err_tx_irq:
> +	if (gh_msgq_has_tx(msgq))
> +		free_irq(msgq->tx_ghrsc.irq, msgq);
> +err_chans:
> +	kfree(msgq->mbox.chans);
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(gunyah_msgq_init);
> +
> +void gunyah_msgq_remove(struct gunyah_msgq *msgq)
> +{
> +	if (gh_msgq_has_tx(msgq))
> +		free_irq(msgq->tx_ghrsc.irq, msgq);


Missing:

+	if (gh_msgq_has_rx(msgq))
+		free_irq(msgq->rx_ghrsc.irq, msgq);


> +
> +	kfree(msgq->mbox.chans);
> +}
> +EXPORT_SYMBOL_GPL(gunyah_msgq_remove);
> +
> +
> +static int __init gh_msgq_init(void)
> +{
> +	if (GH_API_INFO_API_VERSION(gunyah_api.api_info) != GUNYAH_API_V1) {
> +		pr_warn("Unrecognized gunyah version: %llu. Currently supported: %d\n",
> +			GH_API_INFO_API_VERSION(gunyah_api.api_info), GUNYAH_API_V1);
> +		return -ENODEV;
> +	}
> +
> +	return 0;
> +}
> +module_init(gh_msgq_init);
> +
> +static void __exit gh_msgq_exit(void)
> +{
> +}
> +module_exit(gh_msgq_exit);

Not needed

> +
> +MODULE_LICENSE("GPL");
> +MODULE_DESCRIPTION("Gunyah Message Queue Driver");
> diff --git a/drivers/virt/gunyah/Kconfig b/drivers/virt/gunyah/Kconfig
> index 7ac917e0aa3f..f4c822a82f1a 100644
> --- a/drivers/virt/gunyah/Kconfig
> +++ b/drivers/virt/gunyah/Kconfig
> @@ -4,6 +4,8 @@ config GUNYAH
>   	tristate "Gunyah Virtualization drivers"
>   	depends on ARM64
>   	select AUXILIARY_BUS
> +	select MAILBOX
> +	select GUNYAH_MESSAGE_QUEUES
>   	help
>   	  The Gunyah drivers are the helper interfaces that runs in a guest VM
>   	  such as basic inter-VM IPC and signaling mechanisms, and higher level
> diff --git a/include/linux/gunyah.h b/include/linux/gunyah.h
> new file mode 100644
> index 000000000000..0e9709555c79
> --- /dev/null
> +++ b/include/linux/gunyah.h
> @@ -0,0 +1,67 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Copyright (c) 2022 Qualcomm Innovation Center, Inc. All rights reserved.
> + */
> +
> +#ifndef _GUNYAH_H
> +#define _GUNYAH_H
> +
> +#include <linux/mailbox_controller.h>
> +#include <linux/mailbox_client.h>
> +#include <linux/interrupt.h>
> +
> +#include <asm-generic/gunyah.h>
> +
> +/* Follows resource manager's resource types for VM_GET_HYP_RESOURCES */
> +enum gunyah_resource_type {
> +	GUNYAH_RESOURCE_TYPE_BELL_TX	= 0,
> +	GUNYAH_RESOURCE_TYPE_BELL_RX	= 1,
> +	GUNYAH_RESOURCE_TYPE_MSGQ_TX	= 2,
> +	GUNYAH_RESOURCE_TYPE_MSGQ_RX	= 3,
> +	GUNYAH_RESOURCE_TYPE_VCPU	= 4,
> +};
> +
> +struct gunyah_resource {
> +	enum gunyah_resource_type type;
> +	u64 capid;
> +	int irq;
> +};
> +
> +/**
> + * Gunyah Message Queues
> + */
> +
> +#define GH_MSGQ_MAX_MSG_SIZE	240
> +
> +struct gunyah_msgq_tx_data {
> +	size_t length;
> +	bool push;
> +	char data[];
> +};
> +
> +struct gunyah_msgq_rx_data {
> +	size_t length;
> +	char data[GH_MSGQ_MAX_MSG_SIZE];
> +};
> +
> +struct gunyah_msgq {
> +	struct gunyah_resource tx_ghrsc;
> +	struct gunyah_resource rx_ghrsc;
> +
> +	/* msgq private */
> +	int last_status;
> +	struct mbox_controller mbox;
> +	struct tasklet_struct txdone_tasklet;
> +};
> +
> +
> +int gunyah_msgq_init(struct device *parent, struct gunyah_msgq *msgq, struct mbox_client *cl,
> +		     struct gunyah_resource *tx_ghrsc, struct gunyah_resource *rx_ghrsc);
> +void gunyah_msgq_remove(struct gunyah_msgq *msgq);
> +
> +static inline struct mbox_chan *gunyah_msgq_chan(struct gunyah_msgq *msgq)
> +{
> +	return &msgq->mbox.chans[0];
> +}
> +
> +#endif

--
With best wishes
Dmitry