[PATCH v2 02/27] KVM: x86/mmu: Factor out helper to get max mapping size of a memslot

[Sean Christopherson <seanjc@google.com>]

Extract the memslot-related logic of kvm_mmu_max_mapping_level() into a
new helper so that KVMGT can determine whether or not mapping a 2MiB page
into the guest is (dis)allowed per KVM's memslots.

No functional change intended.

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 arch/x86/kvm/mmu/mmu.c          | 21 +++++++++++++++------
 arch/x86/kvm/mmu/mmu_internal.h |  2 ++
 2 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index c8ebe542c565..4685c80e441b 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -3083,20 +3083,29 @@ static int host_pfn_mapping_level(struct kvm *kvm, gfn_t gfn,
 	return level;
 }
 
+int kvm_mmu_max_slot_mapping_level(const struct kvm_memory_slot *slot,
+				   gfn_t gfn, int max_level)
+{
+	struct kvm_lpage_info *linfo;
+
+	for ( ; max_level > PG_LEVEL_4K; max_level--) {
+		linfo = lpage_info_slot(gfn, slot, max_level);
+		if (!linfo->disallow_lpage)
+			break;
+	}
+	return max_level;
+}
+
 int kvm_mmu_max_mapping_level(struct kvm *kvm,
 			      const struct kvm_memory_slot *slot, gfn_t gfn,
 			      int max_level)
 {
-	struct kvm_lpage_info *linfo;
 	int host_level;
 
 	max_level = min(max_level, max_huge_page_level);
-	for ( ; max_level > PG_LEVEL_4K; max_level--) {
-		linfo = lpage_info_slot(gfn, slot, max_level);
-		if (!linfo->disallow_lpage)
-			break;
-	}
+	max_level = kvm_mmu_max_slot_mapping_level(slot, gfn, max_level);
 
+	/* Avoid walking the host page tables if a hugepage is impossible. */
 	if (max_level == PG_LEVEL_4K)
 		return PG_LEVEL_4K;
 
diff --git a/arch/x86/kvm/mmu/mmu_internal.h b/arch/x86/kvm/mmu/mmu_internal.h
index cc58631e2336..9db7fa0b3bf9 100644
--- a/arch/x86/kvm/mmu/mmu_internal.h
+++ b/arch/x86/kvm/mmu/mmu_internal.h
@@ -328,6 +328,8 @@ static inline int kvm_mmu_do_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
 	return r;
 }
 
+int kvm_mmu_max_slot_mapping_level(const struct kvm_memory_slot *slot,
+				   gfn_t gfn, int max_level);
 int kvm_mmu_max_mapping_level(struct kvm *kvm,
 			      const struct kvm_memory_slot *slot, gfn_t gfn,
 			      int max_level);
-- 
2.40.0.rc1.284.g88254d51c5-goog