Re: [RFC PATCH 07/12] arm/sdei: override qemu_irq handler when binding interrupt

[Peter Maydell <peter.maydell@linaro.org>]

On Tue, 24 Sep 2019 at 16:23, Heyi Guo <guoheyi@huawei.com> wrote:
>
> Override qemu_irq handler to support trigger SDEI event transparently
> after guest binds interrupt to SDEI event. We don't have good way to
> get GIC device and to guarantee SDEI device is initialized after GIC,
> so we search GIC in system bus when the first SDEI request happens or
> in VMSTATE post_load().
>
> Signed-off-by: Heyi Guo <guoheyi@huawei.com>
> Cc: Peter Maydell <peter.maydell@linaro.org>
> Cc: Dave Martin <Dave.Martin@arm.com>
> Cc: Marc Zyngier <marc.zyngier@arm.com>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: James Morse <james.morse@arm.com>


> +static void override_qemu_irq(QemuSDEState *s, int32_t event, uint32_t intid)
> +{
> +    qemu_irq irq;
> +    QemuSDE *sde;
> +    CPUState *cs;
> +    int cpu;
> +
> +    /* SPI */
> +    if (intid >= GIC_INTERNAL) {
> +        cs = arm_get_cpu_by_id(0);
> +        irq = qdev_get_gpio_in(s->gic_dev,
> +                               gic_int_to_irq(s->num_irq, intid, 0));
> +        if (irq) {
> +            qemu_irq_intercept_in(&irq, qemu_sdei_irq_handler, 1);
> +        }

I'm not sure what this code is trying to do, but
qemu_irq_intercept_in() is a function for internal use
by the qtest testing infrastructure, so it shouldn't be
used in 'real' QEMU code.

> +        sde = get_sde_no_check(s, event, cs);
> +        sde->irq = irq;
> +        put_sde(sde, cs);
> +        return;
> +    }

> @@ -1042,6 +1152,17 @@ void sdei_handle_request(CPUState *cs, struct kvm_run *run)
>          return;
>      }
>
> +    if (!sde_state->gic_dev) {
> +        /* Search for ARM GIC device */
> +        qbus_walk_children(sysbus_get_default(), dev_walkerfn,
> +                           NULL, NULL, NULL, sde_state);
> +        if (!sde_state->gic_dev) {
> +            error_report("Cannot find ARM GIC device!");
> +            run->hypercall.args[0] = SDEI_NOT_SUPPORTED;
> +            return;
> +        }
> +    }

Walking through the qbus tree looking for particular devices
isn't really something I'd recommend either.

thanks
-- PMM