KVM: X86: Add kvm_read_guest_page_mmu function

This patch adds a function which can read from the guests
physical memory or from the guest's guest physical memory.
This will be used in the two-dimensional page table walker.
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

arch/x86/include/asm/kvm_host.h

@@ -657,6 +657,9 @@ void kvm_queue_exception_e(struct kvm_vcpu *vcpu, unsigned nr, u32 error_code);
 void kvm_requeue_exception(struct kvm_vcpu *vcpu, unsigned nr);
 void kvm_requeue_exception_e(struct kvm_vcpu *vcpu, unsigned nr, u32 error_code);
 void kvm_inject_page_fault(struct kvm_vcpu *vcpu);
+int kvm_read_guest_page_mmu(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
+			    gfn_t gfn, void *data, int offset, int len,
+			    u32 access);
 bool kvm_require_cpl(struct kvm_vcpu *vcpu, int required_cpl);
 
 int kvm_pic_set_irq(void *opaque, int irq, int level);

arch/x86/kvm/x86.c

@@ -369,6 +369,29 @@ bool kvm_require_cpl(struct kvm_vcpu *vcpu, int required_cpl)
 }
 EXPORT_SYMBOL_GPL(kvm_require_cpl);
 
+/*
+ * This function will be used to read from the physical memory of the currently
+ * running guest. The difference to kvm_read_guest_page is that this function
+ * can read from guest physical or from the guest's guest physical memory.
+ */
+int kvm_read_guest_page_mmu(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
+			    gfn_t ngfn, void *data, int offset, int len,
+			    u32 access)
+{
+	gfn_t real_gfn;
+	gpa_t ngpa;
+
+	ngpa     = gfn_to_gpa(ngfn);
+	real_gfn = mmu->translate_gpa(vcpu, ngpa, access);
+	if (real_gfn == UNMAPPED_GVA)
+		return -EFAULT;
+
+	real_gfn = gpa_to_gfn(real_gfn);
+
+	return kvm_read_guest_page(vcpu->kvm, real_gfn, data, offset, len);
+}
+EXPORT_SYMBOL_GPL(kvm_read_guest_page_mmu);
+
 /*
  * Load the pae pdptrs.  Return true is they are all valid.
  */