Re: [PATCH v4 02/17] hw/arm: virt: add GICv2m for the case when ITS is not available

[Pierrick Bouvier]

On 8/4/25 7:23 AM, Mohamed Mediouni wrote:

On Hypervisor.framework for macOS and WHPX for Windows, the provided 
environment is a GICv3 without ITS.

As such, support a GICv3 w/ GICv2m for that scenario.

Signed-off-by: Mohamed Mediouni <moha...@unpredictable.fr>
---
  hw/arm/virt-acpi-build.c | 4 +++-
  hw/arm/virt.c            | 8 ++++++++
  include/hw/arm/virt.h    | 2 ++
  3 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c
index b01fc4f8ef..969fa3f686 100644
--- a/hw/arm/virt-acpi-build.c
+++ b/hw/arm/virt-acpi-build.c
@@ -848,7 +848,9 @@ build_madt(GArray *table_data, BIOSLinker *linker, 
VirtMachineState *vms)
              build_append_int_noprefix(table_data, memmap[VIRT_GIC_ITS].base, 
8);
              build_append_int_noprefix(table_data, 0, 4);    /* Reserved */
          }
-    } else {
+    }
+
+    if (!vms->its && !vms->no_gicv3_with_gicv2m) {
          const uint16_t spi_base = vms->irqmap[VIRT_GIC_V2M] + ARM_SPI_BASE;

/* 5.2.12.16 GIC MSI Frame Structure */

diff --git a/hw/arm/virt.c b/hw/arm/virt.c
index ef6be3660f..5951b331f3 100644
--- a/hw/arm/virt.c
+++ b/hw/arm/virt.c
@@ -953,6 +953,8 @@ static void create_gic(VirtMachineState *vms, MemoryRegion 
*mem)

if (vms->gic_version != VIRT_GIC_VERSION_2 && vms->its) {

          create_its(vms);
+    } else if (vms->gic_version != VIRT_GIC_VERSION_2 && 
!vms->no_gicv3_with_gicv2m) {
+        create_v2m(vms);
      } else if (vms->gic_version == VIRT_GIC_VERSION_2) {
          create_v2m(vms);
      }
@@ -2402,6 +2404,8 @@ static void machvirt_init(MachineState *machine)
      vms->ns_el2_virt_timer_irq = ns_el2_virt_timer_present() &&
          !vmc->no_ns_el2_virt_timer_irq;

+ vms->no_gicv3_with_gicv2m = vmc->no_gicv3_with_gicv2m;

+
      fdt_add_timer_nodes(vms);
      fdt_add_cpu_nodes(vms);

@@ -3410,6 +3414,7 @@ static void virt_instance_init(Object *obj)

      vms->its = true;
      /* Allow ITS emulation if the machine version supports it */
      vms->tcg_its = !vmc->no_tcg_its;
+    vms->no_gicv3_with_gicv2m = false;

/* Default disallows iommu instantiation */

      vms->iommu = VIRT_IOMMU_NONE;
@@ -3462,8 +3467,11 @@ DEFINE_VIRT_MACHINE_AS_LATEST(10, 1)

static void virt_machine_10_0_options(MachineClass *mc)

  {
+    VirtMachineClass *vmc = VIRT_MACHINE_CLASS(OBJECT_CLASS(mc));
+
      virt_machine_10_1_options(mc);
      compat_props_add(mc->compat_props, hw_compat_10_0, hw_compat_10_0_len);
+    vmc->no_gicv3_with_gicv2m = true;
  }
  DEFINE_VIRT_MACHINE(10, 0)

diff --git a/include/hw/arm/virt.h b/include/hw/arm/virt.h

index 365a28b082..725ec18fd2 100644
--- a/include/hw/arm/virt.h
+++ b/include/hw/arm/virt.h
@@ -131,6 +131,7 @@ struct VirtMachineClass {
      bool no_cpu_topology;
      bool no_tcg_lpa2;
      bool no_ns_el2_virt_timer_irq;
+    bool no_gicv3_with_gicv2m;
      bool no_nested_smmu;
  };

@@ -178,6 +179,7 @@ struct VirtMachineState {

      char *oem_id;
      char *oem_table_id;
      bool ns_el2_virt_timer_irq;
+    bool no_gicv3_with_gicv2m;
      CXLState cxl_devices_state;
  };

I'm not an expert about GIC, but this patch looks sane to me.
Reviewed-by: Pierrick Bouvier <pierrick.bouv...@linaro.org>