KVM: MTRR: do not map huge page for non-consistent range

Based on Intel's SDM, mapping huge page which do not have consistent
memory cache for each 4k page will cause undefined behavior

In order to avoiding this kind of undefined behavior, we force to use
4k pages under this case

Signed-off-by: Xiao Guangrong <guangrong.xiao@linux.intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 29 insertions, 0 deletions

diff --git a/arch/x86/kvm/mtrr.c b/arch/x86/kvm/mtrr.c
index 1445c4a..de1d2d8 100644
--- a/arch/x86/kvm/mtrr.c
+++ b/arch/x86/kvm/mtrr.c
@@ -668,3 +668,32 @@ u8 kvm_mtrr_get_guest_memory_type(struct kvm_vcpu *vcpu, gfn_t gfn)
 	return type;
 }
 EXPORT_SYMBOL_GPL(kvm_mtrr_get_guest_memory_type);
+
+bool kvm_mtrr_check_gfn_range_consistency(struct kvm_vcpu *vcpu, gfn_t gfn,
+					  int page_num)
+{
+	struct kvm_mtrr *mtrr_state = &vcpu->arch.mtrr_state;
+	struct mtrr_iter iter;
+	u64 start, end;
+	int type = -1;
+
+	start = gfn_to_gpa(gfn);
+	end = gfn_to_gpa(gfn + page_num);
+	mtrr_for_each_mem_type(&iter, mtrr_state, start, end) {
+		if (type == -1) {
+			type = iter.mem_type;
+			continue;
+		}
+
+		if (type != iter.mem_type)
+			return false;
+	}
+
+	if (!iter.partial_map)
+		return true;
+
+	if (type == -1)
+		return true;
+
+	return type == mtrr_default_type(mtrr_state);
+}