KVM: SVM: Add helper functions for nested SVM

These are helpers for the nested SVM implementation.

- nsvm_printk implements a debug printk variant
- nested_svm_do calls a handler that can accesses gpa-based memory

v3 makes use of the new permission checker
v6 changes:
- streamline nsvm_debug()
- remove printk(KERN_ERR)
- SVME check before CPL check
- give GP error code
- use new EFER constant
Acked-by: Joerg Roedel <joro@8bytes.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>

arch/x86/kvm/svm.c

@@ -50,6 +50,15 @@ MODULE_LICENSE("GPL");
 
 #define DEBUGCTL_RESERVED_BITS (~(0x3fULL))
 
+/* Turn on to get debugging output*/
+/* #define NESTED_DEBUG */
+
+#ifdef NESTED_DEBUG
+#define nsvm_printk(fmt, args...) printk(KERN_INFO fmt, ## args)
+#else
+#define nsvm_printk(fmt, args...) do {} while(0)
+#endif
+
 /* enable NPT for AMD64 and X86 with PAE */
 #if defined(CONFIG_X86_64) || defined(CONFIG_X86_PAE)
 static bool npt_enabled = true;
@@ -1149,6 +1158,82 @@ static int vmmcall_interception(struct vcpu_svm *svm, struct kvm_run *kvm_run)
 	return 1;
 }
 
+static int nested_svm_check_permissions(struct vcpu_svm *svm)
+{
+	if (!(svm->vcpu.arch.shadow_efer & EFER_SVME)
+	    || !is_paging(&svm->vcpu)) {
+		kvm_queue_exception(&svm->vcpu, UD_VECTOR);
+		return 1;
+	}
+
+	if (svm->vmcb->save.cpl) {
+		kvm_inject_gp(&svm->vcpu, 0);
+		return 1;
+	}
+
+       return 0;
+}
+
+static struct page *nested_svm_get_page(struct vcpu_svm *svm, u64 gpa)
+{
+	struct page *page;
+
+	down_read(&current->mm->mmap_sem);
+	page = gfn_to_page(svm->vcpu.kvm, gpa >> PAGE_SHIFT);
+	up_read(&current->mm->mmap_sem);
+
+	if (is_error_page(page)) {
+		printk(KERN_INFO "%s: could not find page at 0x%llx\n",
+		       __func__, gpa);
+		kvm_release_page_clean(page);
+		kvm_inject_gp(&svm->vcpu, 0);
+		return NULL;
+	}
+	return page;
+}
+
+static int nested_svm_do(struct vcpu_svm *svm,
+			 u64 arg1_gpa, u64 arg2_gpa, void *opaque,
+			 int (*handler)(struct vcpu_svm *svm,
+					void *arg1,
+					void *arg2,
+					void *opaque))
+{
+	struct page *arg1_page;
+	struct page *arg2_page = NULL;
+	void *arg1;
+	void *arg2 = NULL;
+	int retval;
+
+	arg1_page = nested_svm_get_page(svm, arg1_gpa);
+	if(arg1_page == NULL)
+		return 1;
+
+	if (arg2_gpa) {
+		arg2_page = nested_svm_get_page(svm, arg2_gpa);
+		if(arg2_page == NULL) {
+			kvm_release_page_clean(arg1_page);
+			return 1;
+		}
+	}
+
+	arg1 = kmap_atomic(arg1_page, KM_USER0);
+	if (arg2_gpa)
+		arg2 = kmap_atomic(arg2_page, KM_USER1);
+
+	retval = handler(svm, arg1, arg2, opaque);
+
+	kunmap_atomic(arg1, KM_USER0);
+	if (arg2_gpa)
+		kunmap_atomic(arg2, KM_USER1);
+
+	kvm_release_page_dirty(arg1_page);
+	if (arg2_gpa)
+		kvm_release_page_dirty(arg2_page);
+
+	return retval;
+}
+
 static int invalid_op_interception(struct vcpu_svm *svm,
 				   struct kvm_run *kvm_run)
 {