Re: [PATCH v11 07/26] mailbox: Add Gunyah message queue mailbox

[Elliot Berman <quic_eberman@quicinc.com>]

On 3/31/2023 7:25 AM, Alex Elder wrote:
> On 3/3/23 7:06 PM, 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.
> 
> I think it's good to reuse existing frameworks, for example, using
> the mailbox abstraction to implement your messaging code.  But I
> find there are some minor mismatches between what you need and
> the way the mailbox code works.
> 
> I'm not really suggesting you change anything, but I'll just say
> it seemed like there were a few spots you needed to do things
> that were slightly awkward in order to satisfy mailbox requirements.
> 
> I'll point out in a few comments what I mean below.
> 
> I'll take one more look at it again next time, but I assume this
> works and I have no other new comments today.
> 
>                      -Alex
> 
>> Signed-off-by: Elliot Berman <quic_eberman@quicinc.com>
>> ---
>>   Documentation/virt/gunyah/message-queue.rst |   8 +
>>   drivers/mailbox/Makefile                    |   2 +
>>   drivers/mailbox/gunyah-msgq.c               | 209 ++++++++++++++++++++
>>   include/linux/gunyah.h                      |  57 ++++++
>>   4 files changed, 276 insertions(+)
>>   create mode 100644 drivers/mailbox/gunyah-msgq.c
>>
>> diff --git a/Documentation/virt/gunyah/message-queue.rst 
>> b/Documentation/virt/gunyah/message-queue.rst
>> index b352918ae54b..70d82a4ef32d 100644
>> --- a/Documentation/virt/gunyah/message-queue.rst
>> +++ b/Documentation/virt/gunyah/message-queue.rst
>> @@ -61,3 +61,11 @@ vIRQ: two TX message queues will have two vIRQs 
>> (and two capability IDs).
>>         |               |         |                 |         
>> |               |
>>         |               |         |                 |         
>> |               |
>>         +---------------+         +-----------------+         
>> +---------------+
>> +
>> +Gunyah message queues are exposed as mailboxes. To create the 
>> mailbox, create
>> +a mbox_client and call `gh_msgq_init()`. On receipt of the RX_READY 
>> interrupt,
>> +all messages in the RX message queue are read and pushed via the 
>> `rx_callback`
>> +of the registered mbox_client.
>> +
>> +.. kernel-doc:: drivers/mailbox/gunyah-msgq.c
>> +   :identifiers: gh_msgq_init
>> 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..1989298653f9
>> --- /dev/null
>> +++ b/drivers/mailbox/gunyah-msgq.c
>> @@ -0,0 +1,209 @@
>> +// SPDX-License-Identifier: GPL-2.0-only
>> +/*
>> + * Copyright (c) 2022-2023 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 
>> gh_msgq, mbox))
>> +
>> +static irqreturn_t gh_msgq_rx_irq_handler(int irq, void *data)
>> +{
>> +    struct gh_msgq *msgq = data;
>> +    struct gh_msgq_rx_data rx_data;
>> +    enum gh_error gh_error;
>> +    bool ready = true;
>> +
>> +    while (ready) {
>> +        gh_error = gh_hypercall_msgq_recv(msgq->rx_ghrsc->capid,
>> +                &rx_data.data, sizeof(rx_data.data),
>> +                &rx_data.length, &ready);
>> +        if (gh_error != GH_ERROR_OK) {
>> +            if (gh_error != GH_ERROR_MSGQUEUE_EMPTY)
>> +                dev_warn(msgq->mbox.dev, "Failed to receive data: 
>> %d\n", gh_error);
>> +            break;
>> +        }
>> +        mbox_chan_received_data(gh_msgq_chan(msgq), &rx_data);
>> +    }
>> +
>> +    return IRQ_HANDLED;
>> +}
>> +
>> +/* Fired when message queue transitions from "full" to "space 
>> available" to send messages */
>> +static irqreturn_t gh_msgq_tx_irq_handler(int irq, void *data)
>> +{
>> +    struct gh_msgq *msgq = data;
>> +
>> +    mbox_chan_txdone(gh_msgq_chan(msgq), 0);
>> +
>> +    return IRQ_HANDLED;
>> +}
>> +
>> +/* Fired after sending message and hypercall told us there was more 
>> space available. */
>> +static void gh_msgq_txdone_tasklet(struct tasklet_struct *tasklet)
>> +{
>> +    struct gh_msgq *msgq = container_of(tasklet, struct gh_msgq, 
>> txdone_tasklet);
>> +
>> +    mbox_chan_txdone(gh_msgq_chan(msgq), msgq->last_ret);
>> +}
>> +
>> +static int gh_msgq_send_data(struct mbox_chan *chan, void *data)
>> +{
>> +    struct gh_msgq *msgq = mbox_chan_to_msgq(chan);
>> +    struct gh_msgq_tx_data *msgq_data = data;
>> +    u64 tx_flags = 0;
>> +    enum gh_error gh_error;
>> +    bool ready;
>> +
>> +    if (msgq_data->push)
>> +        tx_flags |= GH_HYPERCALL_MSGQ_TX_FLAGS_PUSH;
>> +
>> +    gh_error = gh_hypercall_msgq_send(msgq->tx_ghrsc->capid, 
>> msgq_data->length, msgq_data->data,
>> +                        tx_flags, &ready);
>> +
>> +    /**
>> +     * unlikely because Linux tracks state of msgq and should not try to
>> +     * send message when msgq is full.
>> +     */
>> +    if (unlikely(gh_error == GH_ERROR_MSGQUEUE_FULL))
>> +        return -EAGAIN;
>> +
>> +    /**
>> +     * Propagate all other errors to client. If we return error to 
>> mailbox
>> +     * framework, then no other messages can be sent and nobody will 
>> know
>> +     * to retry this message.
> 
> If you weren't using the mailbox framework, would you be
> sending the error to the client in this case?  (I'm just
> curious; it's good to document the behavior if you were
> to return it to the mailbox framework.)
> 
>> +     */
>> +    msgq->last_ret = gh_remap_error(gh_error);
>> +
>> +    /**
>> +     * This message was successfully sent, but message queue isn't 
>> ready to
>> +     * accept more messages because it's now full. Mailbox framework
>> +     * requires that we only report that message was transmitted when
>> +     * we're ready to transmit another message. We'll get that in the 
>> form
>> +     * of tx IRQ once the other side starts to drain the msgq.
> 
> So you are forced to delay reporting the completion
> here because you're using the mailbox framework.
> 
>> +     */
>> +    if (gh_error == GH_ERROR_OK) {
>> +        if (!ready)
>> +            return 0;
>> +    } else
>> +        dev_err(msgq->mbox.dev, "Failed to send data: %d (%d)\n", 
>> gh_error, msgq->last_ret);
>> +
>> +    /**
>> +     * We can send more messages. Mailbox framework requires that tx 
>> done
>> +     * happens asynchronously to sending the message. Gunyah message 
>> queues
>> +     * tell us right away on the hypercall return whether we can send 
>> more
>> +     * messages. To work around this, defer the txdone to a tasklet.
>> +     */
> 
> If you weren't using the mailbox framework, you'd send the next
> message directly rather than scheduling this tasklet to do it.
> 

That's correct for this and the other 2 comments above.

>> +    tasklet_schedule(&msgq->txdone_tasklet);
>> +
>> +    return 0;
>> +}
>> +
>> +static struct mbox_chan_ops gh_msgq_ops = {
>> +    .send_data = gh_msgq_send_data,
>> +};
>> +
>> +/**
>> + * gh_msgq_init() - Initialize a Gunyah message queue with an 
>> mbox_client
>> + * @parent: optional, device parent used for the mailbox controller
>> + * @msgq: Pointer to the gh_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 must be not NULL. Most 
>> message queue use cases come with
>> + * a pair of message queues to facilitate bidirectional 
>> communication. When tx_ghrsc is set,
>> + * the client can send messages with 
>> mbox_send_message(gh_msgq_chan(msgq), msg). When rx_ghrsc
>> + * is set, the mbox_client must register an .rx_callback() and the 
>> message queue driver will
>> + * deliver all available messages upon receiving the RX ready 
>> interrupt. The messages should be
>> + * consumed or copied by the client right away as the gh_msgq_rx_data 
>> will be replaced/destroyed
>> + * after the callback.
>> + *
>> + * Returns - 0 on success, negative otherwise
>> + */
>> +int gh_msgq_init(struct device *parent, struct gh_msgq *msgq, struct 
>> mbox_client *cl,
>> +         struct gh_resource *tx_ghrsc, struct gh_resource *rx_ghrsc)
>> +{
>> +    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 != GH_RESOURCE_TYPE_MSGQ_TX) ||
>> +        (rx_ghrsc && rx_ghrsc->type != GH_RESOURCE_TYPE_MSGQ_RX))
>> +        return -EINVAL;
>> +
>> +    if (!gh_api_has_feature(GH_FEATURE_MSGQUEUE))
>> +        return -EOPNOTSUPP;
>> +
>> +    msgq->tx_ghrsc = tx_ghrsc;
>> +    msgq->rx_ghrsc = rx_ghrsc;
>> +
>> +    msgq->mbox.dev = parent;
>> +    msgq->mbox.ops = &gh_msgq_ops;
>> +    msgq->mbox.num_chans = 1;
>> +    msgq->mbox.txdone_irq = true;
>> +    msgq->mbox.chans = &msgq->mbox_chan;
>> +
>> +    if (msgq->tx_ghrsc) {
>> +        ret = request_irq(msgq->tx_ghrsc->irq, 
>> gh_msgq_tx_irq_handler, 0, "gh_msgq_tx",
>> +                msgq);
>> +        if (ret)
>> +            goto err_chans;
>> +    }
>> +
>> +    if (msgq->rx_ghrsc) {
>> +        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_setup(&msgq->txdone_tasklet, gh_msgq_txdone_tasklet);
>> +
>> +    ret = mbox_controller_register(&msgq->mbox);
>> +    if (ret)
>> +        goto err_rx_irq;
>> +
>> +    ret = mbox_bind_client(gh_msgq_chan(msgq), cl);
>> +    if (ret)
>> +        goto err_mbox;
>> +
>> +    return 0;
>> +err_mbox:
>> +    mbox_controller_unregister(&msgq->mbox);
>> +err_rx_irq:
>> +    if (msgq->rx_ghrsc)
>> +        free_irq(msgq->rx_ghrsc->irq, msgq);
>> +err_tx_irq:
>> +    if (msgq->tx_ghrsc)
>> +        free_irq(msgq->tx_ghrsc->irq, msgq);
>> +err_chans:
>> +    kfree(msgq->mbox.chans);
>> +    return ret;
>> +}
>> +EXPORT_SYMBOL_GPL(gh_msgq_init);
>> +
>> +void gh_msgq_remove(struct gh_msgq *msgq)
>> +{
>> +    tasklet_kill(&msgq->txdone_tasklet);
>> +    mbox_controller_unregister(&msgq->mbox);
>> +
>> +    if (msgq->rx_ghrsc)
>> +        free_irq(msgq->rx_ghrsc->irq, msgq);
>> +
>> +    if (msgq->tx_ghrsc)
>> +        free_irq(msgq->tx_ghrsc->irq, msgq);
>> +
>> +    kfree(msgq->mbox.chans);
>> +}
>> +EXPORT_SYMBOL_GPL(gh_msgq_remove);
>> +
>> +MODULE_LICENSE("GPL");
>> +MODULE_DESCRIPTION("Gunyah Message Queue Driver");
>> diff --git a/include/linux/gunyah.h b/include/linux/gunyah.h
>> index 18cfbf5ee48b..378bec0f2ce1 100644
>> --- a/include/linux/gunyah.h
>> +++ b/include/linux/gunyah.h
>> @@ -8,11 +8,68 @@
>>   #include <linux/bitfield.h>
>>   #include <linux/errno.h>
>> +#include <linux/interrupt.h>
>>   #include <linux/limits.h>
>> +#include <linux/mailbox_controller.h>
>> +#include <linux/mailbox_client.h>
>>   #include <linux/types.h>
>> +/* Follows resource manager's resource types for VM_GET_HYP_RESOURCES */
> 
> I'm not sure what you mean by "Follows" here.  You mean that these are
> the gh_rm_hyp_resource type values that GET_HYP_RESOURCES can return?
> 

Correct. I will say "Matches ... for VM_GET_HYP_RESOURCES RPC" if it 
helps make it clearer.

> Note that gh_resource_type values must fit in an 8 bit field.
> 
>> +enum gh_resource_type {
>> +    GH_RESOURCE_TYPE_BELL_TX    = 0,
>> +    GH_RESOURCE_TYPE_BELL_RX    = 1,
>> +    GH_RESOURCE_TYPE_MSGQ_TX    = 2,
>> +    GH_RESOURCE_TYPE_MSGQ_RX    = 3,
> 
> Fix alignment below.
> 
>> +    GH_RESOURCE_TYPE_VCPU    = 4,
>> +};
>> +
>> +struct gh_resource {
>> +    enum gh_resource_type type;
>> +    u64 capid;
>> +    unsigned int irq;
>> +};
>> +
>> +/**
>> + * Gunyah Message Queues
>> + */
>> +
>> +#define GH_MSGQ_MAX_MSG_SIZE    240
> 
> Maybe insert another tab the before 240.  You later define
> GH_BELL_NONBLOCK that far out, and aligning them will look
> better.
> 
>> +
>> +struct gh_msgq_tx_data {
>> +    size_t length;
>> +    bool push;
>> +    char data[];
>> +};
>> +
>> +struct gh_msgq_rx_data {
>> +    size_t length;
>> +    char data[GH_MSGQ_MAX_MSG_SIZE];
>> +};
>> +
>> +struct gh_msgq {
>> +    struct gh_resource *tx_ghrsc;
>> +    struct gh_resource *rx_ghrsc;
>> +
>> +    /* msgq private */
>> +    int last_ret; /* Linux error, not GH_STATUS_* */
>> +    struct mbox_chan mbox_chan;
>> +    struct mbox_controller mbox;
>> +    struct tasklet_struct txdone_tasklet;
>> +};
>> +
>> +
>> +int gh_msgq_init(struct device *parent, struct gh_msgq *msgq, struct 
>> mbox_client *cl,
>> +             struct gh_resource *tx_ghrsc, struct gh_resource 
>> *rx_ghrsc);
>> +void gh_msgq_remove(struct gh_msgq *msgq);
>> +
>> +static inline struct mbox_chan *gh_msgq_chan(struct gh_msgq *msgq)
>> +{
>> +    return &msgq->mbox.chans[0];
>> +}
>> +
>>   
>> /******************************************************************************/
>>   /* Common arch-independent definitions for Gunyah 
>> hypercalls                  */
>> +
>>   #define GH_CAPID_INVAL    U64_MAX
>>   #define GH_VMID_ROOT_VM    0xff
>