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


From: Philippe Mathieu-Daudé
Subject: Re: [PATCH v2 14/43] hw/intc/i8259: Introduce i8259 proxy "isa-pic"
Date: Mon, 24 Oct 2022 09:35:48 +0200
User-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.3.2

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.



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