Index: head/sys/amd64/include/vmm_instruction_emul.h
===================================================================
--- head/sys/amd64/include/vmm_instruction_emul.h
+++ head/sys/amd64/include/vmm_instruction_emul.h
@@ -103,6 +103,7 @@
  */
 int vm_gla2gpa_nofault(struct vm *vm, int vcpuid, struct vm_guest_paging *paging,
     uint64_t gla, int prot, uint64_t *gpa, int *is_fault);
+#endif /* _KERNEL */
 
 void vie_init(struct vie *vie, const char *inst_bytes, int inst_length);
 
@@ -117,9 +118,17 @@
  * To skip the 'gla' verification for this or any other reason pass
  * in VIE_INVALID_GLA instead.
  */
+#ifdef _KERNEL
 #define	VIE_INVALID_GLA		(1UL << 63)	/* a non-canonical address */
 int vmm_decode_instruction(struct vm *vm, int cpuid, uint64_t gla,
 			   enum vm_cpu_mode cpu_mode, int csd, struct vie *vie);
+#else /* !_KERNEL */
+/*
+ * Permit instruction decoding logic to be compiled outside of the kernel for
+ * rapid iteration and validation.  No GLA validation is performed, obviously.
+ */
+int vmm_decode_instruction(enum vm_cpu_mode cpu_mode, int csd,
+    struct vie *vie);
 #endif	/* _KERNEL */
 
 #endif	/* _VMM_INSTRUCTION_EMUL_H_ */
Index: head/sys/amd64/vmm/vmm_instruction_emul.c
===================================================================
--- head/sys/amd64/vmm/vmm_instruction_emul.c
+++ head/sys/amd64/vmm/vmm_instruction_emul.c
@@ -50,9 +50,14 @@
 
 #include <machine/vmm.h>
 
+#include <err.h>
 #include <assert.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <strings.h>
 #include <vmmapi.h>
 #define	KASSERT(exp,msg)	assert((exp))
+#define	panic(...)		errx(4, __VA_ARGS__)
 #endif	/* _KERNEL */
 
 #include <machine/vmm_instruction_emul.h>
@@ -1896,7 +1901,6 @@
 	return (0);
 }
 
-#ifdef _KERNEL
 void
 vie_init(struct vie *vie, const char *inst_bytes, int inst_length)
 {
@@ -1915,6 +1919,7 @@
 	}
 }
 
+#ifdef _KERNEL
 static int
 pf_error_code(int usermode, int prot, int rsvd, uint64_t pte)
 {
@@ -2189,6 +2194,7 @@
 	vie->num_valid = inst_length;
 	return (0);
 }
+#endif	/* _KERNEL */
 
 static int
 vie_peek(struct vie *vie, uint8_t *x)
@@ -2611,6 +2617,7 @@
 	return (0);
 }
 
+#ifdef _KERNEL
 /*
  * Verify that the 'guest linear address' provided as collateral of the nested
  * page table fault matches with our instruction decoding.
@@ -2702,10 +2709,15 @@
 
 	return (0);
 }
+#endif	/* _KERNEL */
 
 int
+#ifdef _KERNEL
 vmm_decode_instruction(struct vm *vm, int cpuid, uint64_t gla,
 		       enum vm_cpu_mode cpu_mode, int cs_d, struct vie *vie)
+#else
+vmm_decode_instruction(enum vm_cpu_mode cpu_mode, int cs_d, struct vie *vie)
+#endif
 {
 
 	if (decode_prefixes(vie, cpu_mode, cs_d))
@@ -2729,13 +2741,14 @@
 	if (decode_moffset(vie))
 		return (-1);
 
+#ifdef _KERNEL
 	if ((vie->op.op_flags & VIE_OP_F_NO_GLA_VERIFICATION) == 0) {
 		if (verify_gla(vm, cpuid, gla, vie, cpu_mode))
 			return (-1);
 	}
+#endif
 
 	vie->decoded = 1;	/* success */
 
 	return (0);
 }
-#endif	/* _KERNEL */