If trapping WFI from a L2 guest, and that L1 hasn't asked for
such trap, it is very hard to decide when to unblock the vcpu,
as we only have a very partial view on the guest's nested
interrupt state (the L1 hypervisor knows about it, but L0 doesn't).
In such a case, we're better off just returning to the L2 guest
immediately. It isn't wrong from an architecture perspective.
Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
---
arch/arm64/kvm/arm.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 95760ed448bf..d684a2af3406 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -781,6 +781,15 @@ static void kvm_vcpu_sleep(struct kvm_vcpu *vcpu)
*/
void kvm_vcpu_wfi(struct kvm_vcpu *vcpu)
{
+ /*
+ * If we're in nested state and the guest hypervisor does not trap
+ * WFI, we're in a bit of trouble, as we don't have a good handle
+ * on the interrupts that are pending for the guest yet. Revisit
+ * this at some point.
+ */
+ if (vgic_state_is_nested(vcpu))
+ return;
+
/*
* Sync back the state of the GIC CPU interface so that we have
* the latest PMR and group enables. This ensures that
--
2.39.2
