[RFC PATCH 3/8] KVM: x86/mmu: Refactor handling of not-present SPTEs in mmu_set_spte()

[Sean Christopherson <sean.j.christopherson@intel.com>]

Return early from mmu_set_spte() if the new SPTE is not-present so as to
reduce the indentation of the code that performs metadata updates, e.g.
rmap manipulation.  Additional metadata updates will soon follow...

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
 arch/x86/kvm/mmu/mmu.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 82f69a7456004..182f398036248 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -3126,12 +3126,14 @@ static int mmu_set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
 	if (!was_rmapped && is_large_pte(*sptep))
 		++vcpu->kvm->stat.lpages;
 
-	if (is_shadow_present_pte(*sptep)) {
-		if (!was_rmapped) {
-			rmap_count = rmap_add(vcpu, sptep, gfn);
-			if (rmap_count > RMAP_RECYCLE_THRESHOLD)
-				rmap_recycle(vcpu, sptep, gfn);
-		}
+	/* No additional tracking necessary for not-present SPTEs. */
+	if (!is_shadow_present_pte(*sptep))
+		return ret;
+
+	if (!was_rmapped) {
+		rmap_count = rmap_add(vcpu, sptep, gfn);
+		if (rmap_count > RMAP_RECYCLE_THRESHOLD)
+			rmap_recycle(vcpu, sptep, gfn);
 	}
 
 	return ret;
-- 
2.28.0