[PATCH v3 1/6] KVM: x86/mmu: Fix wrong gfn range of tlb flushing in validate_direct_spte()

[Hou Wenlong]

The spte pointing to the children SP is dropped, so the
whole gfn range covered by the children SP should be flushed.
Although, Hyper-V may treat a 1-page flush the same if the
address points to a huge page, it still would be better
to use the correct size of huge page. Also introduce
a helper function to do range-based flushing when a direct
SP is dropped, which would help prevent future buggy use
of kvm_flush_remote_tlbs_with_address() in such case.

Fixes: c3134ce240eed ("KVM: Replace old tlb flush function with new one to flush a specified range.")
Suggested-by: David Matlack <dmatlack@xxxxxxxxxx>
Signed-off-by: Hou Wenlong <houwenlong.hwl@xxxxxxxxxxxx>
---
 arch/x86/kvm/mmu/mmu.c          |  9 ++++++++-
 arch/x86/kvm/mmu/mmu_internal.h | 10 ++++++++++
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index e418ef3ecfcb..ae9f84b0fc64 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -260,6 +260,13 @@ void kvm_flush_remote_tlbs_with_address(struct kvm *kvm,
 	kvm_flush_remote_tlbs_with_range(kvm, &range);
 }
 
+/* Flush all memory mapped by the given direct SP. */
+static void kvm_flush_remote_tlbs_direct_sp(struct kvm *kvm, struct kvm_mmu_page *sp)
+{
+	WARN_ON_ONCE(!sp->role.direct);
+	kvm_flush_remote_tlbs_gfn(kvm, sp->gfn, sp->role.level + 1);
+}
+
 static void mark_mmio_spte(struct kvm_vcpu *vcpu, u64 *sptep, u64 gfn,
 			   unsigned int access)
 {
@@ -2341,7 +2348,7 @@ static void validate_direct_spte(struct kvm_vcpu *vcpu, u64 *sptep,
 			return;
 
 		drop_parent_pte(child, sptep);
-		kvm_flush_remote_tlbs_with_address(vcpu->kvm, child->gfn, 1);
+		kvm_flush_remote_tlbs_direct_sp(vcpu->kvm, child);
 	}
 }
 
diff --git a/arch/x86/kvm/mmu/mmu_internal.h b/arch/x86/kvm/mmu/mmu_internal.h
index 582def531d4d..6651c154f2e0 100644
--- a/arch/x86/kvm/mmu/mmu_internal.h
+++ b/arch/x86/kvm/mmu/mmu_internal.h
@@ -163,8 +163,18 @@ void kvm_mmu_gfn_allow_lpage(const struct kvm_memory_slot *slot, gfn_t gfn);
 bool kvm_mmu_slot_gfn_write_protect(struct kvm *kvm,
 				    struct kvm_memory_slot *slot, u64 gfn,
 				    int min_level);
+
 void kvm_flush_remote_tlbs_with_address(struct kvm *kvm,
 					u64 start_gfn, u64 pages);
+
+/* Flush the given page (huge or not) of guest memory. */
+static inline void kvm_flush_remote_tlbs_gfn(struct kvm *kvm, gfn_t gfn, int level)
+{
+	u64 pages = KVM_PAGES_PER_HPAGE(level);
+
+	kvm_flush_remote_tlbs_with_address(kvm, gfn, pages);
+}
+
 unsigned int pte_list_count(struct kvm_rmap_head *rmap_head);
 
 extern int nx_huge_pages;
-- 
2.31.1