KVM: arm64: vgic-v4: Make the doorbell request robust w.r.t preemption
[ Upstream commit b321c31c9b7b309dcde5e8854b741c8e6a9a05f0 ]
Xiang reports that VMs occasionally fail to boot on GICv4.1 systems when
running a preemptible kernel, as it is possible that a vCPU is blocked
without requesting a doorbell interrupt.
The issue is that any preemption that occurs between vgic_v4_put() and
schedule() on the block path will mark the vPE as nonresident and *not*
request a doorbell irq. This occurs because when the vcpu thread is
resumed on its way to block, vcpu_load() will make the vPE resident
again. Once the vcpu actually blocks, we don't request a doorbell
anymore, and the vcpu won't be woken up on interrupt delivery.
Fix it by tracking that we're entering WFI, and key the doorbell
request on that flag. This allows us not to make the vPE resident
when going through a preempt/schedule cycle, meaning we don't lose
any state.
Cc: [email protected]
Fixes: 8e01d9a396e6 ("KVM: arm64: vgic-v4: Move the GICv4 residency flow to be driven by vcpu_load/put")
Reported-by: Xiang Chen <[email protected]>
Suggested-by: Zenghui Yu <[email protected]>
Tested-by: Xiang Chen <[email protected]>
Co-developed-by: Oliver Upton <[email protected]>
Signed-off-by: Marc Zyngier <[email protected]>
Acked-by: Zenghui Yu <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Oliver Upton <[email protected]>
Signed-off-by: Sasha Levin <[email protected]>
diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
index 4df9e73..1d7d4cff 100644
--- a/include/kvm/arm_vgic.h
+++ b/include/kvm/arm_vgic.h
@@ -429,6 +429,6 @@ int kvm_vgic_v4_unset_forwarding(struct kvm *kvm, int irq,
int vgic_v4_load(struct kvm_vcpu *vcpu);
void vgic_v4_commit(struct kvm_vcpu *vcpu);
-int vgic_v4_put(struct kvm_vcpu *vcpu, bool need_db);
+int vgic_v4_put(struct kvm_vcpu *vcpu);
#endif /* __KVM_ARM_VGIC_H */
