Re: [PATCH v6 09/21] mailbox: Add Gunyah message queue mailbox

[Elliot Berman]

On 10/27/2022 6:55 AM, Pavan Kondeti wrote:
> Hi Elliot,
>
> On Wed, Oct 26, 2022 at 11:58:34AM -0700, 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>
>
> <snip>
>
> > +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;
> > +}
> > +
> > +static void gh_msgq_txdone_tasklet(unsigned long data)
> > +{
> > +	struct gh_msgq *msgq = (struct gh_msgq *)data;
> > +
> > +	mbox_chan_txdone(gh_msgq_chan(msgq), msgq->last_status);
> > +}
> > +
> > +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;
> > +	unsigned long ret;
> > +	bool ready;
> > +
> > +	if (msgq_data->push)
> > +		tx_flags |= GH_HYPERCALL_MSGQ_TX_FLAGS_PUSH;
> > +
> > +	ret = gh_hypercall_msgq_send(msgq->tx_ghrsc->capid, msgq_data->length,
> > +					(uintptr_t)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(ret == 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.
> > +	 */
> > +	msgq->last_status = gh_remap_error(ret);
> > +
> > +	/**
> > +	 * This message was successfully sent, but message queue isn't ready to
> > +	 * receive more messages because it's now full. Mailbox framework
> > +	 * requires that we only report that message was transmitted only 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.
> > +	 */
> > +	if (ret == GH_ERROR_OK && !ready)
> > +		return 0;
> > +
> > +	/**
> > +	 * 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.
> > +	 */
> > +	tasklet_schedule(&msgq->txdone_tasklet);
> > +
>
> Nice comments.
>
> irq_work would be a better choice.
>
> > +	return 0;
> > +}
> > +
> > +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 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(gh_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 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 gunyah_resource *tx_ghrsc, struct gunyah_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 != 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;
> > +
> > +	msgq->mbox.dev = parent;
> > +	msgq->mbox.ops = &gh_msgq_ops;
> > +	msgq->mbox.chans = kcalloc(1, sizeof(*msgq->mbox.chans), GFP_KERNEL);
>
> Error handling missing.
>
> minor nit pick:
>
> If you initialize num_chans to 1 before, then you can use that as the first
> argument to kcalloc() which makes it more readable since you opted for kcalloc()
> instead of kzalloc() there.
>
> > +	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);
>
> If you wish to use tasklets, use tasklet_setup().
>
> > +
> > +	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 (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(gh_msgq_init);
> > +
> > +void gh_msgq_remove(struct gh_msgq *msgq)
> > +{
> > +	if (gh_msgq_has_rx(msgq))
> > +		free_irq(msgq->rx_ghrsc->irq, msgq);
> > +
> > +	if (gh_msgq_has_tx(msgq))
> > +		free_irq(msgq->tx_ghrsc->irq, msgq);
> > +
> > +	kfree(msgq->mbox.chans);
> > +}
> > +EXPORT_SYMBOL_GPL(gh_msgq_remove);
> > +
>
> Is gh_msgq_remove() supposed to undo every thing done in gh_msgq_init()?
> ex: mbox controller and channel are not unregistered.

Ah thanks for catching, updated this as well as rest of your comments.