Re: [PATCH v2 14/43] hw/intc/i8259: Introduce i8259 proxy "isa-pic"

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

Hi Bernhard,

On 22/10/22 17:04, Bernhard Beschow wrote:
> Having an i8259 proxy allows for ISA PICs to be created and wired up in
> southbridges. This is especially interesting for PIIX3 for two reasons:
> First, the southbridge doesn't need to care about the virtualization
> technology used (KVM, TCG, Xen) due to in-IRQs (where devices get
> attached) and out-IRQs (which will trigger the IRQs of the respective
> virtzalization technology) are separated. Second, since the in-IRQs are
> populated with fully initialized qemu_irq's, they can already be wired
> up inside PIIX3.
> 
> Signed-off-by: Bernhard Beschow <shentey@gmail.com>
> ---
>   hw/intc/i8259.c         | 27 +++++++++++++++++++++++++++
>   include/hw/intc/i8259.h | 14 ++++++++++++++
>   2 files changed, 41 insertions(+)

> +static void isapic_set_irq(void *opaque, int irq, int level)
> +{
> +    ISAPICState *s = opaque;
> +
> +    qemu_set_irq(s->out_irqs[irq], level);
> +}
> +
> +static void isapic_init(Object *obj)
> +{
> +    ISAPICState *s = ISA_PIC(obj);
> +
> +    qdev_init_gpio_in(DEVICE(s), isapic_set_irq, ISA_NUM_IRQS);
> +    qdev_init_gpio_out(DEVICE(s), s->out_irqs, ISA_NUM_IRQS);
> +
> +    for (int i = 0; i < ISA_NUM_IRQS; ++i) {
> +        s->in_irqs[i] = qdev_get_gpio_in(DEVICE(s), i);
> +    }
> +}
> +
> +static const TypeInfo isapic_info = {
> +    .name          = TYPE_ISA_PIC,
> +    .parent        = TYPE_ISA_DEVICE,
> +    .instance_size = sizeof(ISAPICState),
> +    .instance_init = isapic_init,
> +};

> --- a/include/hw/intc/i8259.h
> +++ b/include/hw/intc/i8259.h
> @@ -1,6 +1,20 @@
>   #ifndef HW_I8259_H
>   #define HW_I8259_H
>   
> +#include "qom/object.h"
> +#include "hw/isa/isa.h"
> +#include "qemu/typedefs.h"
> +
> +#define TYPE_ISA_PIC "isa-pic"
> +OBJECT_DECLARE_SIMPLE_TYPE(ISAPICState, ISA_PIC)
> +
> +struct ISAPICState {
> +    ISADevice parent_obj;
> +
> +    qemu_irq in_irqs[ISA_NUM_IRQS];
> +    qemu_irq out_irqs[ISA_NUM_IRQS];
> +};

There is nothing I8259 / ISA specific in your model.

What about adding a generic qdev proxy-irq (having a configurable
number of IRQs to proxy)? See for example hw/core/split-irq.c.

Regards,

Phil.