Re: [PATCH v2 2/6] genirq: Allow an interrupt to be marked as 'raw'

Will Deacon
2020-12-10T15:09:24Z

Hi Marc,

On Tue, Nov 24, 2020 at 02:14:45PM +0000, Marc Zyngier wrote:
> Some interrupts (such as the rescheduling IPI) rely on not going through
> the irq_enter()/irq_exit() calls. To distinguish such interrupts, add
> a new IRQ flag that allows the low-level handling code to sidestep the
> enter()/exit() calls.
>
> Only the architecture code is expected to use this. It will do the wrong
> thing on normal interrupts. Note that this is a band-aid until we can
> move to some more correct infrastructure (such as kernel/entry/common.c).
>
> Signed-off-by: Marc Zyngier <maz@kernel.org>
> ---
> include/linux/irq.h | 2 ++
> kernel/irq/Kconfig | 3 +++
> kernel/irq/debugfs.c | 1 +
> kernel/irq/irqdesc.c | 17 ++++++++++++-----
> kernel/irq/settings.h | 15 +++++++++++++++
> 5 files changed, 33 insertions(+), 5 deletions(-)

[...]

> diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c
> index 1a7723604399..f5beee546a6f 100644
> --- a/kernel/irq/irqdesc.c
> +++ b/kernel/irq/irqdesc.c
> @@ -667,10 +667,9 @@ int __handle_domain_irq(struct irq_domain *domain, unsigned int hwirq,
> {
> struct pt_regs *old_regs = set_irq_regs(regs);
> unsigned int irq = hwirq;
> + struct irq_desc *desc;
> int ret = 0;
>
> - irq_enter();
> -
> #ifdef CONFIG_IRQ_DOMAIN
> if (lookup)
> irq = irq_find_mapping(domain, hwirq);
> @@ -680,14 +679,22 @@ int __handle_domain_irq(struct irq_domain *domain, unsigned int hwirq,
> * Some hardware gives randomly wrong interrupts. Rather
> * than crashing, do something sensible.
> */
> - if (unlikely(!irq || irq >= nr_irqs)) {
> + if (unlikely(!irq || irq >= nr_irqs || !(desc = irq_to_desc(irq)))) {
> ack_bad_irq(irq);
> ret = -EINVAL;
> + goto out;
> + }
> +
> + if (IS_ENABLED(CONFIG_ARCH_WANTS_IRQ_RAW) &&
> + unlikely(irq_settings_is_raw(desc))) {
> + generic_handle_irq_desc(desc);

Based on tglx's previous comments, I was expecting to see calls to
__irq_{enter,exit}_raw() around this. Are they hiding somewhere else or
are they not needed?

Will