[PATCH v5 02/36] KVM: arm64: vgic: Rework vgic_is_v3() and add vgic_host_has_gicvX()

Sascha Bischoff
2026-02-26T15:57:07Z

The GIC version checks used to determine host capabilities and guest
configuration have become somewhat conflated (in part due to the
addition of GICv5 support). vgic_is_v3() is a prime example, which
prior to this change has been a combination of guest configuration and
host cabability.

Split out the host capability check from vgic_is_v3(), which now only
checks if the vgic model itself is GICv3. Add two new functions:
vgic_host_has_gicv3() and vgic_host_has_gicv5(). These explicitly
check the host capabilities, i.e., can the host system run a GICvX
guest or not.

The vgic_is_v3() check in vcpu_set_ich_hcr() has been replaced with
vgic_host_has_gicv3() as this only applies on GICv3-capable hardware,
and isn't strictly only applicable for a GICv3 guest (it is actually
vital for vGICv2 on GICv3 hosts).

Signed-off-by: Sascha Bischoff <sascha.bischoff@arm.com>
---
arch/arm64/kvm/sys_regs.c | 2 +-
arch/arm64/kvm/vgic/vgic-v3.c | 2 +-
arch/arm64/kvm/vgic/vgic.h | 17 +++++++++++++----
3 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index b4e78958ede12..270f1c927c35b 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -1982,7 +1982,7 @@ static u64 sanitise_id_aa64pfr0_el1(const struct kvm_vcpu *vcpu, u64 val)
val |= SYS_FIELD_PREP_ENUM(ID_AA64PFR0_EL1, CSV3, IMP);
}

- if (vgic_is_v3(vcpu->kvm)) {
+ if (vgic_host_has_gicv3()) {
val &= ~ID_AA64PFR0_EL1_GIC_MASK;
val |= SYS_FIELD_PREP_ENUM(ID_AA64PFR0_EL1, GIC, IMP);
}
diff --git a/arch/arm64/kvm/vgic/vgic-v3.c b/arch/arm64/kvm/vgic/vgic-v3.c
index 386ddf69a9c51..7fc2e0deccff2 100644
--- a/arch/arm64/kvm/vgic/vgic-v3.c
+++ b/arch/arm64/kvm/vgic/vgic-v3.c
@@ -499,7 +499,7 @@ void vcpu_set_ich_hcr(struct kvm_vcpu *vcpu)
{
struct vgic_v3_cpu_if *vgic_v3 = &vcpu->arch.vgic_cpu.vgic_v3;

- if (!vgic_is_v3(vcpu->kvm))
+ if (!vgic_host_has_gicv3())
return;

/* Hide GICv3 sysreg if necessary */
diff --git a/arch/arm64/kvm/vgic/vgic.h b/arch/arm64/kvm/vgic/vgic.h
index c9b3bb07e483c..0bb8fa10bb4ef 100644
--- a/arch/arm64/kvm/vgic/vgic.h
+++ b/arch/arm64/kvm/vgic/vgic.h
@@ -454,15 +454,24 @@ void vgic_v3_put_nested(struct kvm_vcpu *vcpu);
void vgic_v3_handle_nested_maint_irq(struct kvm_vcpu *vcpu);
void vgic_v3_nested_update_mi(struct kvm_vcpu *vcpu);

-static inline bool vgic_is_v3_compat(struct kvm *kvm)
+static inline bool vgic_is_v3(struct kvm *kvm)
+{
+ return kvm->arch.vgic.vgic_model == KVM_DEV_TYPE_ARM_VGIC_V3;
+}
+
+static inline bool vgic_host_has_gicv3(void)
{
- return cpus_have_final_cap(ARM64_HAS_GICV5_CPUIF) &&
+ /*
+ * Either the host is a native GICv3, or it is GICv5 with
+ * FEAT_GCIE_LEGACY.
+ */
+ return kvm_vgic_global_state.type == VGIC_V3 ||
kvm_vgic_global_state.has_gcie_v3_compat;
}

-static inline bool vgic_is_v3(struct kvm *kvm)
+static inline bool vgic_host_has_gicv5(void)
{
- return kvm_vgic_global_state.type == VGIC_V3 || vgic_is_v3_compat(kvm);
+ return kvm_vgic_global_state.type == VGIC_V5;
}

int vgic_its_debug_init(struct kvm_device *dev);
--
2.34.1