[PATCH 04/11] ARM: Allow IPIs to be handled as normal interrupts

Marc Zyngier
2020-05-19T16:18:49Z

In order to deal with IPIs as normal interrupts, let's add
a new way to register them with the architecture code.

set_smp_ipi_range() takes a range of interrupts, and allows
the arch code to request them as if the were normal interrupts.
A standard handler is then called by the core IRQ code to deal
with the IPI.

This means that we don't need to call irq_enter/irq_exit, and
that we don't need to deal with set_irq_regs either. So let's
move the dispatcher into its own function, and leave handle_IPI()
as a compatibility function.

On the sending side, let's make use of ipi_send_mask, which
already exists for this purpose.

Signed-off-by: Marc Zyngier <maz@kernel.org>
---
arch/arm/Kconfig | 1 +
arch/arm/include/asm/smp.h | 5 ++
arch/arm/kernel/smp.c | 97 ++++++++++++++++++++++++++++++++------
3 files changed, 88 insertions(+), 15 deletions(-)

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index c77c93c485a0..0caaba9bf880 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -48,6 +48,7 @@ config ARM
select GENERIC_ARCH_TOPOLOGY if ARM_CPU_TOPOLOGY
select GENERIC_ATOMIC64 if CPU_V7M || CPU_V6 || !CPU_32v6K || !AEABI
select GENERIC_CLOCKEVENTS_BROADCAST if SMP
+ select GENERIC_IRQ_IPI if SMP
select GENERIC_CPU_AUTOPROBE
select GENERIC_EARLY_IOREMAP
select GENERIC_IDLE_POLL_SETUP
diff --git a/arch/arm/include/asm/smp.h b/arch/arm/include/asm/smp.h
index a91f21e3c5b5..0e29730295ca 100644
--- a/arch/arm/include/asm/smp.h
+++ b/arch/arm/include/asm/smp.h
@@ -45,6 +45,11 @@ extern void smp_init_cpus(void);
*/
extern void set_smp_cross_call(void (*)(const struct cpumask *, unsigned int));

+/*
+ * Register IPI interrupts with the arch SMP code
+ */
+extern void set_smp_ipi_range(int ipi_base, int nr_ipi);
+
/*
* Called from platform specific assembly code, this is the
* secondary CPU entry point.
diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
index 46e1be9e57a8..618641978a5b 100644
--- a/arch/arm/kernel/smp.c
+++ b/arch/arm/kernel/smp.c
@@ -79,10 +79,19 @@ enum ipi_msg_type {
*/
};

+static int ipi_irq_base;
+static int nr_ipi = NR_IPI;
+static struct irq_desc *ipi_desc[NR_IPI];
+
+static void ipi_setup(int cpu);
+static void ipi_teardown(int cpu);
+
static DECLARE_COMPLETION(cpu_running);

static struct smp_operations smp_ops __ro_after_init;

+static void ipi_setup(int cpu);
+
void __init smp_set_ops(const struct smp_operations *ops)
{
if (ops)
@@ -308,6 +317,8 @@ void arch_cpu_idle_dead(void)

local_irq_disable();

+ ipi_teardown(cpu);
+
/*
* Flush the data out of the L1 cache for this CPU. This must be
* before the completion to ensure that data is safely written out
@@ -424,6 +435,8 @@ asmlinkage void secondary_start_kernel(void)

notify_cpu_starting(cpu);

+ ipi_setup(cpu);
+
calibrate_delay();

smp_store_cpu_info(cpu);
@@ -629,10 +642,9 @@ asmlinkage void __exception_irq_entry do_IPI(int ipinr, struct pt_regs *regs)
handle_IPI(ipinr, regs);
}

-void handle_IPI(int ipinr, struct pt_regs *regs)
+static void do_handle_IPI(int ipinr)
{
unsigned int cpu = smp_processor_id();
- struct pt_regs *old_regs = set_irq_regs(regs);

if ((unsigned)ipinr < NR_IPI) {
trace_ipi_entry_rcuidle(ipi_types[ipinr]);
@@ -645,9 +657,7 @@ void handle_IPI(int ipinr, struct pt_regs *regs)

#ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
case IPI_TIMER:
- irq_enter();
tick_receive_broadcast();
- irq_exit();
break;
#endif

@@ -656,36 +666,26 @@ void handle_IPI(int ipinr, struct pt_regs *regs)
break;

case IPI_CALL_FUNC:
- irq_enter();
generic_smp_call_function_interrupt();
- irq_exit();
break;

case IPI_CPU_STOP:
- irq_enter();
ipi_cpu_stop(cpu);
- irq_exit();
break;

#ifdef CONFIG_IRQ_WORK
case IPI_IRQ_WORK:
- irq_enter();
irq_work_run();
- irq_exit();
break;
#endif

case IPI_COMPLETION:
- irq_enter();
ipi_complete(cpu);
- irq_exit();
break;

case IPI_CPU_BACKTRACE:
printk_nmi_enter();
- irq_enter();
- nmi_cpu_backtrace(regs);
- irq_exit();
+ nmi_cpu_backtrace(get_irq_regs());
printk_nmi_exit();
break;

@@ -697,9 +697,76 @@ void handle_IPI(int ipinr, struct pt_regs *regs)

if ((unsigned)ipinr < NR_IPI)
trace_ipi_exit_rcuidle(ipi_types[ipinr]);
+}
+
+/* Legacy version, should go away once all irqchips have been converted */
+void handle_IPI(int ipinr, struct pt_regs *regs)
+{
+ struct pt_regs *old_regs = set_irq_regs(regs);
+
+ irq_enter();
+ do_handle_IPI(ipinr);
+ irq_exit();
+
set_irq_regs(old_regs);
}

+static irqreturn_t ipi_handler(int irq, void *data)
+{
+ do_handle_IPI(irq - ipi_irq_base);
+ return IRQ_HANDLED;
+}
+
+static void ipi_send(const struct cpumask *target, unsigned int ipi)
+{
+ __ipi_send_mask(ipi_desc[ipi], target);
+}
+
+static void ipi_setup(int cpu)
+{
+ if (ipi_irq_base) {
+ int i;
+
+ for (i = 0; i < nr_ipi; i++)
+ enable_percpu_irq(ipi_irq_base + i, 0);
+ }
+}
+
+static void ipi_teardown(int cpu)
+{
+ if (ipi_irq_base) {
+ int i;
+
+ for (i = 0; i < nr_ipi; i++)
+ disable_percpu_irq(ipi_irq_base + i);
+ }
+}
+
+void __init set_smp_ipi_range(int ipi_base, int n)
+{
+ int i;
+
+ WARN_ON(n < NR_IPI);
+ nr_ipi = min(n, NR_IPI);
+
+ for (i = 0; i < nr_ipi; i++) {
+ int err;
+
+ err = request_percpu_irq(ipi_base + i, ipi_handler,
+ "IPI", &irq_stat);
+ WARN_ON(err);
+
+ ipi_desc[i] = irq_to_desc(ipi_base + i);
+ irq_set_status_flags(ipi_base + i, IRQ_NO_ACCOUNTING);
+ }
+
+ ipi_irq_base = ipi_base;
+ set_smp_cross_call(ipi_send);
+
+ /* Setup the boot CPU immediately */
+ ipi_setup(smp_processor_id());
+}
+
void smp_send_reschedule(int cpu)
{
smp_cross_call(cpumask_of(cpu), IPI_RESCHEDULE);
--
2.26.2