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.
Fix it by consistently requesting a doorbell irq in the vcpu put path if
the vCPU is blocking. While this technically means we could drop the
early doorbell irq request in kvm_vcpu_wfi(), deliberately leave it
intact such that vCPU halt polling can properly detect the wakeup
condition before actually scheduling out a vCPU.
Cc: stable@xxxxxxxxxxxxxxx
Fixes: 8e01d9a396e6 ("KVM: arm64: vgic-v4: Move the GICv4 residency flow to be driven by vcpu_load/put")
Reported-by: Xiang Chen <chenxiang66@xxxxxxxxxxxxx>
Tested-by: Xiang Chen <chenxiang66@xxxxxxxxxxxxx>
Signed-off-by: Oliver Upton <oliver.upton@xxxxxxxxx>
---
arch/arm64/kvm/vgic/vgic-v3.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/arm64/kvm/vgic/vgic-v3.c b/arch/arm64/kvm/vgic/vgic-v3.c
index c3b8e132d599..8c467e9f4f11 100644
--- a/arch/arm64/kvm/vgic/vgic-v3.c
+++ b/arch/arm64/kvm/vgic/vgic-v3.c
@@ -749,7 +749,7 @@ void vgic_v3_put(struct kvm_vcpu *vcpu)
{
struct vgic_v3_cpu_if *cpu_if = &vcpu->arch.vgic_cpu.vgic_v3;
- WARN_ON(vgic_v4_put(vcpu, false));
+ WARN_ON(vgic_v4_put(vcpu, kvm_vcpu_is_blocking(vcpu)));
vgic_v3_vmcr_sync(vcpu);
--
2.41.0.255.g8b1d071c50-goog
