[PATCH] KVM: arm64: vgic-v4: Consistently request doorbell irq for blocking vCPU

[Oliver Upton <oliver.upton@linux.dev>]

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@vger.kernel.org
Fixes: 8e01d9a396e6 ("KVM: arm64: vgic-v4: Move the GICv4 residency flow to be driven by vcpu_load/put")
Reported-by: Xiang Chen <chenxiang66@hisilicon.com>
Tested-by: Xiang Chen <chenxiang66@hisilicon.com>
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
---
 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