Re: [RFC PATCH v3 35/37] kvx: Add IPI driver

Thomas Gleixner
2024-07-27T14:08:43Z

On Mon, Jul 22 2024 at 11:41, ysionneau@kalrayinc.com wrote:
> +/*
> + * IPI controller can signal RM and PE0 -> 15
> + * In order to restrict that to the PE, write the corresponding mask

This comment is undecodable

> + */
> +#define KVX_IPI_CPU_MASK (~0xFFFF)
> +
> +/* A collection of single bit ipi messages. */
> +static DEFINE_PER_CPU_ALIGNED(unsigned long, ipi_data);
> +
> +struct kvx_ipi_ctrl {
> + void __iomem *regs;
> + unsigned int ipi_irq;
> +};
> +
> +static struct kvx_ipi_ctrl kvx_ipi_controller;
> +
> +void kvx_ipi_send(const struct cpumask *mask, unsigned int operation)

Why is this global? It's only used in this file, no?

> +{
> + const unsigned long *maskb = cpumask_bits(mask);
> + unsigned long flags;
> + int cpu;
> +
> + /* Set operation that must be done by receiver */
> + for_each_cpu(cpu, mask)
> + set_bit(operation, &per_cpu(ipi_data, cpu));
> +
> + /* Commit the write before sending IPI */
> + smp_wmb();
> +
> + local_irq_save(flags);
> +
> + WARN_ON(*maskb & KVX_IPI_CPU_MASK);

> +#define KVX_IPI_CPU_MASK (~0xFFFF)

This means the system is limited to 16 CPUs, right?

How should a bit >= NR_CPUs be set in a valid cpu mask? Also above you
happily iterate the full cpumask. This does not make sense.

> + writel(*maskb, kvx_ipi_controller.regs + IPI_INTERRUPT_OFFSET);
> +
> + local_irq_restore(flags);
> +}
> +
> +static int kvx_ipi_starting_cpu(unsigned int cpu)
> +{
> + enable_percpu_irq(kvx_ipi_controller.ipi_irq, IRQ_TYPE_NONE);
> +
> + return 0;
> +}
> +
> +static int kvx_ipi_dying_cpu(unsigned int cpu)
> +{
> + disable_percpu_irq(kvx_ipi_controller.ipi_irq);
> +
> + return 0;
> +}
> +
> +static irqreturn_t ipi_irq_handler(int irq, void *dev_id)
> +{
> + unsigned long *pending_ipis = &per_cpu(ipi_data, smp_processor_id());

this_cpu_ptr() ?

> + while (true) {
> + unsigned long ops = xchg(pending_ipis, 0);
> +
> + if (!ops)
> + return IRQ_HANDLED;
> +
> + handle_IPI(ops);
> + }

for (ops = xchg(pending_ipis, 0); ops; ops = xchg(pending_ipis, 0))
handle_IPI(ops);

Hmm?

> + return IRQ_HANDLED;
> +}
> +
> +int __init kvx_ipi_ctrl_init(struct device_node *node,
> + struct device_node *parent)
> +{
> + int ret;
> + unsigned int ipi_irq;
> + void __iomem *ipi_base;
> +
> + BUG_ON(!node);
> +
> + ipi_base = of_iomap(node, 0);

What's the point of this ipi_base indirection? Just use controller.regs
directly.

> + BUG_ON(!ipi_base);
> +
> + kvx_ipi_controller.regs = ipi_base;
> +
> + /* Init mask for interrupts to PE0 -> PE15 */
> + writel(KVX_IPI_CPU_MASK, kvx_ipi_controller.regs + IPI_MASK_OFFSET);
> +
> + ipi_irq = irq_of_parse_and_map(node, 0);
> + if (!ipi_irq) {
> + pr_err("Failed to parse irq: %d\n", ipi_irq);
> + return -EINVAL;
> + }
> +
> + ret = request_percpu_irq(ipi_irq, ipi_irq_handler,
> + "kvx_ipi", &kvx_ipi_controller);
> + if (ret) {
> + pr_err("can't register interrupt %d (%d)\n",
> + ipi_irq, ret);
> + return ret;
> + }
> + kvx_ipi_controller.ipi_irq = ipi_irq;
> +
> + ret = cpuhp_setup_state(CPUHP_AP_IRQ_KVX_STARTING,
> + "kvx/ipi:online",
> + kvx_ipi_starting_cpu,
> + kvx_ipi_dying_cpu);
> + if (ret < 0) {
> + pr_err("Failed to setup hotplug state");

That leaves the half initialized IPI handler around.

> + return ret;

Thanks,

tglx