arm64: KVM: Use static keys for selecting the GIC backend

Currently GIC backend is selected via alternative framework and this
is fine. We are going to introduce vgic-v3 to 32-bit world and there
we don't have patching framework in hand, so we can either check
support for GICv3 every time we need to choose which backend to use or
try to optimise it by using static keys. The later looks quite
promising because we can share logic involved in selecting GIC backend
between architectures if both uses static keys.

This patch moves arm64 from alternative to static keys framework for
selecting GIC backend. For that we embed static key into vgic_global
and enable the key during vgic initialisation based on what has
already been exposed by the host GIC driver.

Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>

2 files changed, 5 insertions, 1 deletions

diff --git a/virt/kvm/arm/vgic/vgic-init.c b/virt/kvm/arm/vgic/vgic-init.c
index 83777c1cbae0..8cebfbc19e90 100644
--- a/virt/kvm/arm/vgic/vgic-init.c
+++ b/virt/kvm/arm/vgic/vgic-init.c
@@ -405,6 +405,10 @@ int kvm_vgic_hyp_init(void)
                 break;
         case GIC_V3:
                 ret = vgic_v3_probe(gic_kvm_info);
+                if (!ret) {
+                        static_branch_enable(&kvm_vgic_global_state.gicv3_cpuif);
+                        kvm_info("GIC system register CPU interface enabled\n");
+                }
                 break;
         default:
                 ret = -ENODEV;
diff --git a/virt/kvm/arm/vgic/vgic.c b/virt/kvm/arm/vgic/vgic.c
index e83b7fe4baae..8a529a732941 100644
--- a/virt/kvm/arm/vgic/vgic.c
+++ b/virt/kvm/arm/vgic/vgic.c
@@ -29,7 +29,7 @@
 #define DEBUG_SPINLOCK_BUG_ON(p)
 #endif
 
-struct vgic_global __section(.hyp.text) kvm_vgic_global_state;
+struct vgic_global __section(.hyp.text) kvm_vgic_global_state = {.gicv3_cpuif = STATIC_KEY_FALSE_INIT,};
 
 /*
  * Locking order is always: