Re: [PATCH 4/6] irq: add a new generic IPI handling code to irq core

Jiang Liu
2015-09-23T16:50:50Z

On 2015/9/23 22:49, Qais Yousef wrote:
> Add a generic mechanism to dynamically allocate an IPI.
>
> With this change the user can call irq_reserve_ipi() to dynamically allocate an
> IPI and use the associate virq to send one to 1 or more cpus.
>
> No irq_get_irq_hwcfg() as I hope we can provide an implementation without
> hardware specific part. Hopefully I'm not being too optimistic :)
>
> Signed-off-by: Qais Yousef <qais.yousef@imgtec.com>
> ---
> include/linux/irqdomain.h | 4 ++
> kernel/irq/irqdomain.c | 161 +++++++++++++++++++++++++++++++++++++++++++++-
> 2 files changed, 164 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/irqdomain.h b/include/linux/irqdomain.h
> index 76a0e7aaa8df..4bdd7b48d205 100644
> --- a/include/linux/irqdomain.h
> +++ b/include/linux/irqdomain.h
> @@ -329,6 +329,10 @@ extern struct ipi_virq *irq_domain_find_ipi_virq(struct irq_domain *d,
> extern int irq_domain_ipi_virq_add_hwirq(struct ipi_virq *v,
> struct ipi_hwirq *h);
> extern struct ipi_hwirq *irq_domain_ipi_virq_rm_hwirq(struct ipi_virq *v);
> +extern unsigned int irq_reserve_ipi(struct irq_domain *domain,
> + const struct cpumask *dest, void *devid);
> +extern void irq_destroy_ipi(unsigned int irq, void *devid);
> +extern void irq_send_ipi(unsigned int irq, const struct cpumask *dest, void *devid);
>
> /* V2 interfaces to support hierarchy IRQ domains. */
> extern struct irq_data *irq_domain_get_irq_data(struct irq_domain *domain,
> diff --git a/kernel/irq/irqdomain.c b/kernel/irq/irqdomain.c
> index 6d911fc8fa52..d38d78a994ca 100644
> --- a/kernel/irq/irqdomain.c
> +++ b/kernel/irq/irqdomain.c
> @@ -873,7 +873,7 @@ struct ipi_virq *irq_domain_find_ipi_virq(struct irq_domain *d,
> * returns a pointer to ipi_virq struct on success and NULL on failure
> */
> static struct ipi_virq *irq_domain_alloc_ipi_virq(unsigned int virq,
> - struct cpumask *cpumask, void *devid)
> + const struct cpumask *cpumask, void *devid)
> {
> struct ipi_virq *v;
>
> @@ -942,6 +942,165 @@ struct ipi_hwirq *irq_domain_ipi_virq_rm_hwirq(struct ipi_virq *v)
> return h;
> }
>
> +/**
> + * irq_reserve_ipi() - setup an IPI to destination cpumask
> + * @domain: IPI domain
> + * @dest: cpumask of cpus to receive the IPI
> + * @devid: devid that requested the reservation
> + *
> + * Allocate a virq that can be used to send IPI to any CPU in dest mask.
> + *
> + * On success it'll return linux irq number and 0 on failure
> + */
> +unsigned int irq_reserve_ipi(struct irq_domain *domain,
> + const struct cpumask *dest, void *devid)
Hi Qais,
I have caught the idea why we need "dest" here. Per my
understanding, IPI could be sent to any active CPUs and the target
CPUs are specified when calling send_ipi(). What's the benefit or
usage to use "dest" to define a possible target scope here? And
how cpu hotplug?
Thanks!
Gerry

> +{
> + int virq, ret;
> + unsigned int nr_irqs;
> + struct ipi_virq *v;
> +
> + if (domain == NULL)
> + domain = irq_default_domain; /* need a separate ipi_default_domain? */
> +
> + if (domain == NULL) {
> + pr_warn("Must provide a valid IPI domain!\n");
> + return 0;
> + }
> +
> + if (!irq_domain_is_ipi(domain)) {
> + pr_warn("Not an IPI domain!\n");
> + return 0;
> + }
> +
> + if (cpumask_empty(dest)) {
> + pr_warn("Can't reserve IPI due to empty cpumask\n");
> + return 0;
> + }
> +
> + /* always allocate a virq per cpu */
> + nr_irqs = cpumask_weight(dest);
> +
> + virq = irq_domain_alloc_descs(-1, nr_irqs, 0, NUMA_NO_NODE);
> + if (virq <= 0) {
> + pr_warn("Can't reserve IPI, failed to alloc descs\n");
> + return 0;
> + }
> +
> + v = irq_domain_alloc_ipi_virq(virq, dest, devid);
> + if (!v) {
> + pr_warn("Can't reserve IPI, failed to alloc ipi_virq\n");
> + goto free_descs;
> + }
> +
> + /* we are reusing hierarchy alloc function, should we create another one? */
> + virq = __irq_domain_alloc_irqs(domain, virq, nr_irqs, NUMA_NO_NODE,
> + v, true);
> + if (virq <= 0) {
> + pr_warn("Can't reserve IPI, failed to alloc irqs\n");
> + goto free_ipi;
> + }
> +
> + ret = irq_domain_add_ipi_virq(domain, v);
> + if (ret) {
> + pr_warn("Can't reserve IPI, failed to add ipi_virq\n");
> + goto free_ipi;
> + }
> +
> + return virq;
> +
> +free_ipi:
> + irq_domain_free_ipi_virq(v);
> +free_descs:
> + irq_free_descs(virq, nr_irqs);
> + return 0;
> +}
> +
> +/**
> + * irq_destroy_ipi() - unreserve an IPI that was previously allocated
> + * @irq: linux irq number to be destroyed
> + * @devid: devid that reserved the IPI
> + *
> + * Return an IPI allocated with irq_reserve_ipi() to the system.
> + */
> +void irq_destroy_ipi(unsigned int irq, void *devid)
> +{
> + struct irq_data *irq_data = irq_get_irq_data(irq);
> + struct irq_domain *domain;
> + struct ipi_virq *v;
> +
> + if (!irq || !irq_data)
> + return;
> +
> + domain = irq_data->domain;
> + if (WARN_ON(domain == NULL))
> + return;
> +
> + if (!irq_domain_is_ipi(domain)) {
> + pr_warn("Not an IPI domain!\n");
> + return;
> + }
> +
> + v = irq_domain_find_ipi_virq(domain, irq);
> + if (!v)
> + return;
> +
> + if (v->devid != devid) {
> + pr_warn("Only the device that allocated the IPI can destroy it\n");
> + return;
> + }
> +
> + irq_domain_free_irqs(irq, cpumask_weight(&v->cpumask));
> +
> + v = irq_domain_rm_ipi_virq(domain, irq);
> + irq_domain_free_ipi_virq(v);
> +}
> +
> +/**
> + * irq_send_ipi() - send an IPI to target CPU(s)
> + * @irq: linux irq number from irq_reserve_ipi()
> + * @dest: dest CPU(s), must be the same or a subset of the mask past to
> + * irq_reserve_ipi()
> + * @devid: devid that reserved the IPI
> + *
> + * Sends an IPI to all cpus in dest mask
> + */
> +void irq_send_ipi(unsigned int irq, const struct cpumask *dest, void *devid)
> +{
> + struct irq_data *irq_data = irq_get_irq_data(irq);
> + struct irq_domain *domain;
> + struct ipi_virq *v;
> + struct ipi_hwirq *h;
> +
> + if (!irq || !irq_data)
> + return;
> +
> + domain = irq_data->domain;
> + if (WARN_ON(domain == NULL))
> + return;
> +
> + if (!irq_domain_is_ipi(domain)) {
> + pr_warn("Not an IPI domain!\n");
> + return;
> + }
> +
> + v = irq_domain_find_ipi_virq(domain, irq);
> + if (!v)
> + return;
> +
> + if (v->devid != devid) {
> + pr_warn("Only the device that allocated the IPI can send one\n");
> + return;
> + }
> +
> + if (!cpumask_intersects(&v->cpumask, dest))
> + return;
> +
> + list_for_each_entry(h, &v->mapped_hwirq, link) {
> + if (cpumask_intersects(&h->cpumask, dest))
> + domain->ops->send_ipi(h->hwirq);
> + }
> +}
> +
> #ifdef CONFIG_IRQ_DOMAIN_HIERARCHY
> /**
> * irq_domain_add_hierarchy - Add a irqdomain into the hierarchy
>