Re: [RFC PATCH] hw/arm/virt: Support NMI injection

[Gavin Shan]

On 1/29/20 6:57 PM, Julien Thierry wrote:
> On 1/29/20 3:46 AM, Gavin Shan wrote:
> > On 1/28/20 7:29 PM, Julien Thierry wrote:

.../...

> > Julien, thanks for the explanation. The question we're not sure if NMI should
> > be injected on receiving HMP/QMP "nmi" command. It means it's not clear what
> > behavior we should have for this command on ARM. However, I have one more
> > unrelated question: "pseudo" NMI on ARM64 should be PPI? I mean SPI can't
> > be "pseudo" NMI.
>
> I'm not sure I understand why you say "SPI can't be "pseudo" NMI". Currently both PPI and 
> SPI are supported in the "pseudo" NMI scheme. Do you think that should not be the case? If so, can 
> you elaborate?
>
> Thanks,

Julien, NMI interrupt is connected to the system by request_nmi() where we have
a check as below. -EINVAL will be returned from request_nmi() on those 
interrupts
whose descriptors aren't marked with IRQ_NOAUTOEN. SPI falls into this category.
Please refer to below code snippet extracted from gic_irq_domain_map() for more
details.

kernel/irq/manage.c::request_nmi()

int request_nmi(unsigned int irq, irq_handler_t handler,
                unsigned long irqflags, const char *name, void *dev_id)
{
        :
        if (!desc || irq_settings_can_autoenable(desc) ||
            !irq_settings_can_request(desc) ||
            WARN_ON(irq_settings_is_per_cpu_devid(desc)) ||
            !irq_supports_nmi(desc))
                return -EINVAL;
        :
}


acpi_register_gsi
   irq_create_fwspec_mapping
      irq_domain_alloc_irqs
         __irq_domain_alloc_irqs
            irq_domain_alloc_irqs_hierarchy
               gic_irq_domain_alloc                  # irq_domain_ops::alloc
                  gic_irq_domain_map

drivers/irqchip/irq-gic-v3.c::gic_irq_domain_map()

static int gic_irq_domain_map(struct irq_domain *d, unsigned int irq,
                              irq_hw_number_t hw)
{
        :
       switch (__get_intid_range(hw)) {
        case PPI_RANGE:
        case EPPI_RANGE:
                irq_set_percpu_devid(irq);
                irq_domain_set_info(d, irq, hw, chip, d->host_data,
                                    handle_percpu_devid_irq, NULL, NULL);
                irq_set_status_flags(irq, IRQ_NOAUTOEN);                      
<<<< this flag
                break;

        case SPI_RANGE:
        case ESPI_RANGE:
                irq_domain_set_info(d, irq, hw, chip, d->host_data,
                                    handle_fasteoi_irq, NULL, NULL);
                irq_set_probe(irq);
                irqd_set_single_target(irq_desc_get_irq_data(irq_to_desc(irq)));
                break;
           :
        }
        :
}

Thanks,
Gavin