[PATCH v4 19/49] KVM: arm64: Compute vgic state irrespective of the number of interrupts

[Marc Zyngier]

As we are going to rely on the [G]ICH_HCR{,_EL2} register to be
programmed with MI information at all times, slightly de-optimise
the flush/sync code to always be called. This is rather lightweight
when no interrupts are in flight.

Tested-by: Fuad Tabba <tabba at google.com>
Signed-off-by: Marc Zyngier <maz at kernel.org>
---
 arch/arm64/kvm/vgic/vgic.c | 35 ++---------------------------------
 1 file changed, 2 insertions(+), 33 deletions(-)

diff --git a/arch/arm64/kvm/vgic/vgic.c b/arch/arm64/kvm/vgic/vgic.c
index 7ee253a9fb77e..39346baa2677c 100644
--- a/arch/arm64/kvm/vgic/vgic.c
+++ b/arch/arm64/kvm/vgic/vgic.c
@@ -985,8 +985,6 @@ static inline void vgic_save_state(struct kvm_vcpu *vcpu)
 /* Sync back the hardware VGIC state into our emulation after a guest's run. */
 void kvm_vgic_sync_hwstate(struct kvm_vcpu *vcpu)
 {
-	int used_lrs;
-
 	/* If nesting, emulate the HW effect from L0 to L1 */
 	if (vgic_state_is_nested(vcpu)) {
 		vgic_v3_sync_nested(vcpu);
@@ -996,20 +994,10 @@ void kvm_vgic_sync_hwstate(struct kvm_vcpu *vcpu)
 	if (vcpu_has_nv(vcpu))
 		vgic_v3_nested_update_mi(vcpu);
 
-	/* An empty ap_list_head implies used_lrs == 0 */
-	if (list_empty(&vcpu->arch.vgic_cpu.ap_list_head))
-		return;
-
 	if (can_access_vgic_from_kernel())
 		vgic_save_state(vcpu);
 
-	if (!static_branch_unlikely(&kvm_vgic_global_state.gicv3_cpuif))
-		used_lrs = vcpu->arch.vgic_cpu.vgic_v2.used_lrs;
-	else
-		used_lrs = vcpu->arch.vgic_cpu.vgic_v3.used_lrs;
-
-	if (used_lrs)
-		vgic_fold_lr_state(vcpu);
+	vgic_fold_lr_state(vcpu);
 	vgic_prune_ap_list(vcpu);
 }
 
@@ -1053,29 +1041,10 @@ void kvm_vgic_flush_hwstate(struct kvm_vcpu *vcpu)
 	if (vcpu_has_nv(vcpu))
 		vgic_v3_nested_update_mi(vcpu);
 
-	/*
-	 * If there are no virtual interrupts active or pending for this
-	 * VCPU, then there is no work to do and we can bail out without
-	 * taking any lock.  There is a potential race with someone injecting
-	 * interrupts to the VCPU, but it is a benign race as the VCPU will
-	 * either observe the new interrupt before or after doing this check,
-	 * and introducing additional synchronization mechanism doesn't change
-	 * this.
-	 *
-	 * Note that we still need to go through the whole thing if anything
-	 * can be directly injected (GICv4).
-	 */
-	if (list_empty(&vcpu->arch.vgic_cpu.ap_list_head) &&
-	    !vgic_supports_direct_irqs(vcpu->kvm))
-		return;
-
 	DEBUG_SPINLOCK_BUG_ON(!irqs_disabled());
 
-	if (!list_empty(&vcpu->arch.vgic_cpu.ap_list_head)) {
-		raw_spin_lock(&vcpu->arch.vgic_cpu.ap_list_lock);
+	scoped_guard(raw_spinlock, &vcpu->arch.vgic_cpu.ap_list_lock)
 		vgic_flush_lr_state(vcpu);
-		raw_spin_unlock(&vcpu->arch.vgic_cpu.ap_list_lock);
-	}
 
 	if (can_access_vgic_from_kernel())
 		vgic_restore_state(vcpu);
-- 
2.47.3