Index: sys/kern/subr_pcpu.c
===================================================================
--- sys/kern/subr_pcpu.c
+++ sys/kern/subr_pcpu.c
@@ -95,6 +95,7 @@
 	cpu_pcpu_init(pcpu, cpuid, size);
 	pcpu->pc_rm_queue.rmq_next = &pcpu->pc_rm_queue;
 	pcpu->pc_rm_queue.rmq_prev = &pcpu->pc_rm_queue;
+	pcpu->pc_zpcpu_offset = zpcpu_offset(cpuid);
 }
 
 void
Index: sys/sys/pcpu.h
===================================================================
--- sys/sys/pcpu.h
+++ sys/sys/pcpu.h
@@ -189,7 +189,7 @@
 	long		pc_cp_time[CPUSTATES];	/* statclock ticks */
 	struct device	*pc_device;
 	void		*pc_netisr;		/* netisr SWI cookie */
-	int		pc_unused1;		/* unused field */
+	u_int		pc_zpcpu_offset;	/* Offset into zpcpu allocs */
 	int		pc_domain;		/* Memory domain. */
 	struct rm_queue	pc_rm_queue;		/* rmlock list of trackers */
 	uintptr_t	pc_dynamic;		/* Dynamic per-cpu data area */
@@ -227,14 +227,18 @@
 #endif
 #define	curproc		(curthread->td_proc)
 
+#define zpcpu_offset(cpu)	(UMA_PCPU_ALLOC_SIZE * cpu)
+_Static_assert(zpcpu_offset(MAXCPU - 1) < (1<<20),
+    "zpcpu_offset may need to be revisited");
+
 /* Accessor to elements allocated via UMA_ZONE_PCPU zone. */
 #define zpcpu_get(base) ({								\
-	__typeof(base) _ptr = (void *)((char *)(base) + UMA_PCPU_ALLOC_SIZE * curcpu);	\
+	__typeof(base) _ptr = (void *)((char *)(base) + PCPU_GET(zpcpu_offset));	\
 	_ptr;										\
 })
 
 #define zpcpu_get_cpu(base, cpu) ({							\
-	__typeof(base) _ptr = (void *)((char *)(base) +	UMA_PCPU_ALLOC_SIZE * cpu);	\
+	__typeof(base) _ptr = (void *)((char *)(base) +	zpcpu_offset(cpu));		\
 	_ptr;										\
 })