KVM: export information about NPT to generic x86 code

The generic x86 code has to know if the specific implementation uses Nested
Paging. In the generic code Nested Paging is called Two Dimensional Paging
(TDP) to avoid confusion with (future) TDP implementations of other vendors.
This patch exports the availability of TDP to the generic x86 code.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>

arch/x86/kvm/mmu.c

@@ -32,6 +32,15 @@
 #include <asm/cmpxchg.h>
 #include <asm/io.h>
 
+/*
+ * When setting this variable to true it enables Two-Dimensional-Paging
+ * where the hardware walks 2 page tables:
+ * 1. the guest-virtual to guest-physical
+ * 2. while doing 1. it walks guest-physical to host-physical
+ * If the hardware supports that we don't need to do shadow paging.
+ */
+static bool tdp_enabled = false;
+
 #undef MMU_DEBUG
 
 #undef AUDIT
@@ -1582,6 +1591,12 @@ out:
 }
 EXPORT_SYMBOL_GPL(kvm_mmu_page_fault);
 
+void kvm_enable_tdp(void)
+{
+	tdp_enabled = true;
+}
+EXPORT_SYMBOL_GPL(kvm_enable_tdp);
+
 static void free_mmu_pages(struct kvm_vcpu *vcpu)
 {
 	struct kvm_mmu_page *sp;

arch/x86/kvm/svm.c

@@ -426,8 +426,10 @@ static __init int svm_hardware_setup(void)
 		npt_enabled = false;
 	}
 
-	if (npt_enabled)
+	if (npt_enabled) {
 		printk(KERN_INFO "kvm: Nested Paging enabled\n");
+		kvm_enable_tdp();
+	}
 
 	return 0;
 

include/asm-x86/kvm_host.h

@@ -493,6 +493,8 @@ int kvm_fix_hypercall(struct kvm_vcpu *vcpu);
 
 int kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gva_t gva, u32 error_code);
 
+void kvm_enable_tdp(void);
+
 int load_pdptrs(struct kvm_vcpu *vcpu, unsigned long cr3);
 int complete_pio(struct kvm_vcpu *vcpu);