arm/arm64: KVM: Initialize the vgic on-demand when injecting IRQs

commit ca7d9c829d419c06e450afa5f785d58198c37caa upstream.

Userspace assumes that it can wire up IRQ injections after having
created all VCPUs and after having created the VGIC, but potentially
before starting the first VCPU.  This can currently lead to lost IRQs
because the state of that IRQ injection is not stored anywhere and we
don't return an error to userspace.

We haven't seen this problem manifest itself yet, presumably because
guests reset the devices on boot, but this could cause issues with
migration and other non-standard startup configurations.

Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Shannon Zhao <shannon.zhao@linaro.org>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>

diff --git a/virt/kvm/arm/vgic.c b/virt/kvm/arm/vgic.c
index 12c10f26901f6e32b42893ef192ed671d78b5165..9a8c18301b7a47d11811e8721c1852a214f544a9 100644 (file)
--- a/virt/kvm/arm/vgic.c
+++ b/virt/kvm/arm/vgic.c
@@ -1693,16 +1693,26 @@ out:
 int kvm_vgic_inject_irq(struct kvm *kvm, int cpuid, unsigned int irq_num,
                        bool level)
 {
+       int ret = 0;
        int vcpu_id;
 
-       if (likely(vgic_initialized(kvm))) {
-               vcpu_id = vgic_update_irq_pending(kvm, cpuid, irq_num, level);
-               if (vcpu_id >= 0)
-                       /* kick the specified vcpu */
-                       kvm_vcpu_kick(kvm_get_vcpu(kvm, vcpu_id));
+       if (unlikely(!vgic_initialized(kvm))) {
+               mutex_lock(&kvm->lock);
+               ret = vgic_init(kvm);
+               mutex_unlock(&kvm->lock);
+
+               if (ret)
+                       goto out;
        }
 
-       return 0;
+       vcpu_id = vgic_update_irq_pending(kvm, cpuid, irq_num, level);
+       if (vcpu_id >= 0) {
+               /* kick the specified vcpu */
+               kvm_vcpu_kick(kvm_get_vcpu(kvm, vcpu_id));
+       }
+
+out:
+       return ret;
 }
 
 static irqreturn_t vgic_maintenance_handler(int irq, void *data)