ARM: Allow IPIs to be handled as normal interrupts

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.

One of the major difference is that we end up, in some cases
(such as when performing IRQ time accounting on the scheduler
IPI), end up with nested irq_enter()/irq_exit() pairs.
Other than the (relatively small) overhead, there should be
no consequences to it (these pairs are designed to nest
correctly, and the accounting shouldn't be off).

Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>

1 files changed, 5 insertions, 0 deletions

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
@@ -46,6 +46,11 @@ 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.
  */