From fb77bb2a0ff253e6c370ec7dc1afa45b2ecd8d2e Mon Sep 17 00:00:00 2001 From: Fuad Tabba Date: Mon, 12 Oct 2026 17:15:22 +0100 Subject: [PATCH] KVM: arm64: Validate the host-provided vgic model in pKVM EL2 copies vgic_model from the host's struct kvm unchecked, and the nVHE world switch dispatches on it with no cpucap guard. A host writing KVM_DEV_TYPE_ARM_VGIC_V5 makes EL2 access GICv5 CPU interface registers that are UNDEFINED without FEAT_GCIE, and panics the hypervisor on any GICv3 machine. Accept only GICv3, the one model pKVM supports, and force anything else to 0, as for a VM with no in-kernel irqchip. EL2 reads the model only to pick the GICv5 world switch and to emulate GICv3 CPU interface accesses, and the host's own copy is left alone. Fixes: 9b8e3d4ca0e73 ("KVM: arm64: gic-v5: Implement GICv5 load/put and save/restore") Reviewed-by: Suzuki K Poulose Signed-off-by: Fuad Tabba Link: https://patch.msgid.link/20261012161524.4016464-4-fuad.tabba@linux.dev Signed-off-by: Marc Zyngier --- arch/arm64/kvm/hyp/nvhe/pkvm.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/arch/arm64/kvm/hyp/nvhe/pkvm.c b/arch/arm64/kvm/hyp/nvhe/pkvm.c index 459bd9eb7e4b..a9d0e9470919 100644 --- a/arch/arm64/kvm/hyp/nvhe/pkvm.c +++ b/arch/arm64/kvm/hyp/nvhe/pkvm.c @@ -340,13 +340,19 @@ static void pkvm_init_features_from_host(struct pkvm_hyp_vm *hyp_vm, const struc { struct kvm *kvm = &hyp_vm->kvm; unsigned long host_arch_flags = READ_ONCE(host_kvm->arch.flags); + u32 vgic_model = READ_ONCE(host_kvm->arch.vgic.vgic_model); DECLARE_BITMAP(allowed_features, KVM_VCPU_MAX_FEATURES); /* CTR_EL0 is always under host control, even for protected VMs. */ hyp_vm->kvm.arch.ctr_el0 = host_kvm->arch.ctr_el0; - /* Preserve the vgic model so that GICv3 emulation works */ - hyp_vm->kvm.arch.vgic.vgic_model = host_kvm->arch.vgic.vgic_model; + /* + * pKVM runs only GICv3. Anything else becomes 0, the model of a VM + * with no in-kernel irqchip, which keeps EL2 off the GICv5 registers. + */ + if (vgic_model != KVM_DEV_TYPE_ARM_VGIC_V3) + vgic_model = 0; + hyp_vm->kvm.arch.vgic.vgic_model = vgic_model; /* No restrictions for non-protected VMs. */ if (!kvm_vm_is_protected(kvm)) {