[PATCH v4 47/66] KVM: arm64: nv: Don't load the GICv4 context on entering a nested guest

[Marc Zyngier]

When entering a nested guest (vgic_state_is_nested() == true),
special care must be taken *not* to make the vPE resident, as
these are interrupts targetting the L1 guest, and not any
nested guest.

By not making the vPE resident, we guarantee that the delivery
of an vLPI will result in a doorbell, forcing an exit from the
nested guest and a switch to the L1 guest to handle the interrupt.

Signed-off-by: Marc Zyngier <maz at kernel.org>
---
 arch/arm64/kvm/vgic/vgic-v3.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kvm/vgic/vgic-v3.c b/arch/arm64/kvm/vgic/vgic-v3.c
index d8991feadff3..1c8601bb810a 100644
--- a/arch/arm64/kvm/vgic/vgic-v3.c
+++ b/arch/arm64/kvm/vgic/vgic-v3.c
@@ -734,8 +734,8 @@ void vgic_v3_load(struct kvm_vcpu *vcpu)
 
 	if (vgic_state_is_nested(vcpu))
 		vgic_v3_load_nested(vcpu);
-
-	WARN_ON(vgic_v4_load(vcpu));
+	else
+		WARN_ON(vgic_v4_load(vcpu));
 }
 
 void vgic_v3_vmcr_sync(struct kvm_vcpu *vcpu)
@@ -753,6 +753,12 @@ void vgic_v3_put(struct kvm_vcpu *vcpu)
 {
 	struct vgic_v3_cpu_if *cpu_if = &vcpu->arch.vgic_cpu.vgic_v3;
 
+	/*
+	 * vgic_v4_put will do nothing if we were not resident. This
+	 * covers both the cases where we've blocked (we already have
+	 * done a vgic_v4_put) and when running a nested guest (the
+	 * vPE was never resident in order to generate a doorbell).
+	 */
 	WARN_ON(vgic_v4_put(vcpu, false));
 
 	vgic_v3_vmcr_sync(vcpu);
-- 
2.29.2