[PATCH v7 51/68] KVM: arm64: nv: Deal with broken VGIC on maintenance interrupt delivery

[Marc Zyngier]

Normal, non-nesting KVM deals with maintenance interrupt in a very
simple way: we don't even try to handle it and just turn it off
as soon as we exit, long before the kernel can handle it.

However, with NV, we rely on the actual handling of the interrupt
to leave it active and pass it down to the L1 guest hypervisor
(we effectively treat it as an assigned interrupt, just like the
timer).

This doesn't work with something like the Apple M2, which doesn't
have an active state that allows the interrupt to be masked.

Instead, just disable the vgic after having taken the interrupt and
injected a virtual interrupt. This is enough for the guest to make
forward progress, but will limit its ability to handle further
interrupts until it next exits (IAR will always report "spurious").

Oh well.

Signed-off-by: Marc Zyngier <maz at kernel.org>
---
 arch/arm64/kvm/vgic/vgic-v3-nested.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/arm64/kvm/vgic/vgic-v3-nested.c b/arch/arm64/kvm/vgic/vgic-v3-nested.c
index 755e4819603a..919275b94625 100644
--- a/arch/arm64/kvm/vgic/vgic-v3-nested.c
+++ b/arch/arm64/kvm/vgic/vgic-v3-nested.c
@@ -225,4 +225,7 @@ void vgic_v3_handle_nested_maint_irq(struct kvm_vcpu *vcpu)
 		kvm_vgic_inject_irq(vcpu->kvm, vcpu->vcpu_id,
 				    vcpu->kvm->arch.vgic.maint_irq, state, vcpu);
 	}
+
+	if (unlikely(kvm_vgic_global_state.no_hw_deactivation))
+		sysreg_clear_set_s(SYS_ICH_HCR_EL2, ICH_HCR_EN, 0);
 }
-- 
2.34.1