KVM: x86/mmu: Fix wrong start gfn of tlb flushing with range

When a spte is dropped, the start gfn of tlb flushing should be the gfn
of spte not the base gfn of SP which contains the spte. Also introduce a
helper function to do range-based flushing when a spte is dropped, which
would help prevent future buggy use of
kvm_flush_remote_tlbs_with_address() in such case.

Fixes: c3134ce ("KVM: Replace old tlb flush function with new one to flush a specified range.")
Suggested-by: David Matlack <dmatlack@google.com>
Signed-off-by: Hou Wenlong <houwenlong.hwl@antgroup.com>
Link: https://lore.kernel.org/r/72ac2169a261976f00c1703e88cda676dfb960f5.1665214747.git.houwenlong.hwl@antgroup.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

arch/x86/kvm/mmu/mmu.c

@@ -269,6 +269,17 @@ void kvm_flush_remote_tlbs_with_address(struct kvm *kvm,
 	kvm_flush_remote_tlbs_with_range(kvm, &range);
 }
 
+static gfn_t kvm_mmu_page_get_gfn(struct kvm_mmu_page *sp, int index);
+
+/* Flush the range of guest memory mapped by the given SPTE. */
+static void kvm_flush_remote_tlbs_sptep(struct kvm *kvm, u64 *sptep)
+{
+	struct kvm_mmu_page *sp = sptep_to_sp(sptep);
+	gfn_t gfn = kvm_mmu_page_get_gfn(sp, spte_index(sptep));
+
+	kvm_flush_remote_tlbs_gfn(kvm, gfn, sp->role.level);
+}
+
 static void mark_mmio_spte(struct kvm_vcpu *vcpu, u64 *sptep, u64 gfn,
 			   unsigned int access)
 {
@@ -1187,8 +1198,7 @@ static void drop_large_spte(struct kvm *kvm, u64 *sptep, bool flush)
 	drop_spte(kvm, sptep);
 
 	if (flush)
-		kvm_flush_remote_tlbs_with_address(kvm, sp->gfn,
-			KVM_PAGES_PER_HPAGE(sp->role.level));
+		kvm_flush_remote_tlbs_sptep(kvm, sptep);
 }
 
 /*
@@ -1639,8 +1649,7 @@ static void __rmap_add(struct kvm *kvm,
 		kvm->stat.max_mmu_rmap_size = rmap_count;
 	if (rmap_count > RMAP_RECYCLE_THRESHOLD) {
 		kvm_zap_all_rmap_sptes(kvm, rmap_head);
-		kvm_flush_remote_tlbs_with_address(
-				kvm, sp->gfn, KVM_PAGES_PER_HPAGE(sp->role.level));
+		kvm_flush_remote_tlbs_gfn(kvm, gfn, sp->role.level);
 	}
 }
 
@@ -6521,8 +6530,7 @@ static bool kvm_mmu_zap_collapsible_spte(struct kvm *kvm,
 			kvm_zap_one_rmap_spte(kvm, rmap_head, sptep);
 
 			if (kvm_available_flush_tlb_with_range())
-				kvm_flush_remote_tlbs_with_address(kvm, sp->gfn,
-					KVM_PAGES_PER_HPAGE(sp->role.level));
+				kvm_flush_remote_tlbs_sptep(kvm, sptep);
 			else
 				need_tlb_flush = 1;
 

arch/x86/kvm/mmu/paging_tmpl.h

@@ -927,8 +927,7 @@ static void FNAME(invlpg)(struct kvm_vcpu *vcpu, gva_t gva, hpa_t root_hpa)
 
 			mmu_page_zap_pte(vcpu->kvm, sp, sptep, NULL);
 			if (is_shadow_present_pte(old_spte))
-				kvm_flush_remote_tlbs_with_address(vcpu->kvm,
-					sp->gfn, KVM_PAGES_PER_HPAGE(sp->role.level));
+				kvm_flush_remote_tlbs_sptep(vcpu->kvm, sptep);
 
 			if (!rmap_can_add(vcpu))
 				break;