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

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Date:   Fri, 23 Dec 2022 00:57:14 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Zhenyu Wang <zhenyuw@...ux.intel.com>,
        Zhi Wang <zhi.a.wang@...el.com>
Cc:     kvm@...r.kernel.org, intel-gvt-dev@...ts.freedesktop.org,
        intel-gfx@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Yan Zhao <yan.y.zhao@...el.com>,
        Ben Gardon <bgardon@...gle.com>
Subject: [PATCH 02/27] KVM: x86/mmu: Factor out helper to get max mapping size
 of a memslot

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@...gle.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 254bc46234e0..ca7428b68eba 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -3064,20 +3064,29 @@ 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 ac00bfbf32f6..b078c29e5674 100644
--- a/arch/x86/kvm/mmu/mmu_internal.h
+++ b/arch/x86/kvm/mmu/mmu_internal.h
@@ -314,6 +314,8 @@ 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);
-- 
2.39.0.314.g84b9a713c41-goog