[PATCH kvmtool v3 3/6] arm64: nested: add support for setting maintenance IRQ

Andre Przywara
2025-07-29T09:58:02Z

Uses the new VGIC KVM device attribute to set the maintenance IRQ.
This is fixed to use PPI 9, as a platform decision made by kvmtool,
matching the SBSA recommendation.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
---
arm64/arm-cpu.c | 3 ++-
arm64/gic.c | 21 ++++++++++++++++++++-
arm64/include/kvm/gic.h | 2 +-
3 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/arm64/arm-cpu.c b/arm64/arm-cpu.c
index 69bb2cb2c..1e456f2c6 100644
--- a/arm64/arm-cpu.c
+++ b/arm64/arm-cpu.c
@@ -14,7 +14,8 @@ static void generate_fdt_nodes(void *fdt, struct kvm *kvm)
{
int timer_interrupts[4] = {13, 14, 11, 10};

- gic__generate_fdt_nodes(fdt, kvm->cfg.arch.irqchip);
+ gic__generate_fdt_nodes(fdt, kvm->cfg.arch.irqchip,
+ kvm->cfg.arch.nested_virt);
timer__generate_fdt_nodes(fdt, kvm, timer_interrupts);
pmu__generate_fdt_nodes(fdt, kvm);
}
diff --git a/arm64/gic.c b/arm64/gic.c
index b0d3a1abb..7461b0f3f 100644
--- a/arm64/gic.c
+++ b/arm64/gic.c
@@ -11,6 +11,8 @@

#define IRQCHIP_GIC 0

+#define GIC_MAINT_IRQ 9
+
static int gic_fd = -1;
static u64 gic_redists_base;
static u64 gic_redists_size;
@@ -302,10 +304,15 @@ static int gic__init_gic(struct kvm *kvm)

int lines = irq__get_nr_allocated_lines();
u32 nr_irqs = ALIGN(lines, 32) + GIC_SPI_IRQ_BASE;
+ u32 maint_irq = GIC_MAINT_IRQ + 16; /* PPI */
struct kvm_device_attr nr_irqs_attr = {
.group = KVM_DEV_ARM_VGIC_GRP_NR_IRQS,
.addr = (u64)(unsigned long)&nr_irqs,
};
+ struct kvm_device_attr maint_irq_attr = {
+ .group = KVM_DEV_ARM_VGIC_GRP_MAINT_IRQ,
+ .addr = (u64)(unsigned long)&maint_irq,
+ };
struct kvm_device_attr vgic_init_attr = {
.group = KVM_DEV_ARM_VGIC_GRP_CTRL,
.attr = KVM_DEV_ARM_VGIC_CTRL_INIT,
@@ -325,6 +332,13 @@ static int gic__init_gic(struct kvm *kvm)
return ret;
}

+ if (kvm->cfg.arch.nested_virt &&
+ !ioctl(gic_fd, KVM_HAS_DEVICE_ATTR, &maint_irq_attr)) {
+ ret = ioctl(gic_fd, KVM_SET_DEVICE_ATTR, &maint_irq_attr);
+ if (ret)
+ return ret;
+ }
+
irq__routing_init(kvm);

if (!ioctl(gic_fd, KVM_HAS_DEVICE_ATTR, &vgic_init_attr)) {
@@ -342,7 +356,7 @@ static int gic__init_gic(struct kvm *kvm)
}
late_init(gic__init_gic)

-void gic__generate_fdt_nodes(void *fdt, enum irqchip_type type)
+void gic__generate_fdt_nodes(void *fdt, enum irqchip_type type, bool nested)
{
const char *compatible, *msi_compatible = NULL;
u64 msi_prop[2];
@@ -350,6 +364,8 @@ void gic__generate_fdt_nodes(void *fdt, enum irqchip_type type)
cpu_to_fdt64(ARM_GIC_DIST_BASE), cpu_to_fdt64(ARM_GIC_DIST_SIZE),
0, 0, /* to be filled */
};
+ u32 maint_irq[3] = {cpu_to_fdt32(1), cpu_to_fdt32(GIC_MAINT_IRQ),
+ cpu_to_fdt32(0xff04)};

switch (type) {
case IRQCHIP_GICV2M:
@@ -377,6 +393,9 @@ void gic__generate_fdt_nodes(void *fdt, enum irqchip_type type)
_FDT(fdt_property_cell(fdt, "#interrupt-cells", GIC_FDT_IRQ_NUM_CELLS));
_FDT(fdt_property(fdt, "interrupt-controller", NULL, 0));
_FDT(fdt_property(fdt, "reg", reg_prop, sizeof(reg_prop)));
+ if (nested)
+ _FDT(fdt_property(fdt, "interrupts", maint_irq,
+ sizeof(maint_irq)));
_FDT(fdt_property_cell(fdt, "phandle", PHANDLE_GIC));
_FDT(fdt_property_cell(fdt, "#address-cells", 2));
_FDT(fdt_property_cell(fdt, "#size-cells", 2));
diff --git a/arm64/include/kvm/gic.h b/arm64/include/kvm/gic.h
index ad8bcbf21..1541a5824 100644
--- a/arm64/include/kvm/gic.h
+++ b/arm64/include/kvm/gic.h
@@ -36,7 +36,7 @@ struct kvm;
int gic__alloc_irqnum(void);
int gic__create(struct kvm *kvm, enum irqchip_type type);
int gic__create_gicv2m_frame(struct kvm *kvm, u64 msi_frame_addr);
-void gic__generate_fdt_nodes(void *fdt, enum irqchip_type type);
+void gic__generate_fdt_nodes(void *fdt, enum irqchip_type type, bool nested);
u32 gic__get_fdt_irq_cpumask(struct kvm *kvm);

int gic__add_irqfd(struct kvm *kvm, unsigned int gsi, int trigger_fd,
--
2.25.1