Index: head/sys/arm64/arm64/machdep.c
===================================================================
--- head/sys/arm64/arm64/machdep.c
+++ head/sys/arm64/arm64/machdep.c
@@ -108,6 +108,7 @@
 int64_t dcache_line_size;	/* The minimum D cache line size */
 int64_t icache_line_size;	/* The minimum I cache line size */
 int64_t idcache_line_size;	/* The minimum cache line size */
+int64_t dczva_line_size;	/* The size of cache line the dc zva zeroes */
 
 static void
 cpu_startup(void *dummy)
@@ -129,16 +130,6 @@
 	return (0);
 }
 
-void
-bzero(void *buf, size_t len)
-{
-	uint8_t *p;
-
-	p = buf;
-	while(len-- > 0)
-		*p++ = 0;
-}
-
 int
 fill_regs(struct thread *td, struct reg *regs)
 {
@@ -800,8 +791,9 @@
 static void
 cache_setup(void)
 {
-	int dcache_line_shift, icache_line_shift;
+	int dcache_line_shift, icache_line_shift, dczva_line_shift;
 	uint32_t ctr_el0;
+	uint32_t dczid_el0;
 
 	ctr_el0 = READ_SPECIALREG(ctr_el0);
 
@@ -815,6 +807,17 @@
 	icache_line_size = sizeof(int) << icache_line_shift;
 
 	idcache_line_size = MIN(dcache_line_size, icache_line_size);
+
+	dczid_el0 = READ_SPECIALREG(dczid_el0);
+
+	/* Check if dc zva is not prohibited */
+	if (dczid_el0 & DCZID_DZP)
+		dczva_line_size = 0;
+	else {
+		/* Same as with above calculations */
+		dczva_line_shift = DCZID_BS_SIZE(dczid_el0);
+		dczva_line_size = sizeof(int) << dczva_line_shift;
+	}
 }
 
 void
Index: head/sys/arm64/include/armreg.h
===================================================================
--- head/sys/arm64/include/armreg.h
+++ head/sys/arm64/include/armreg.h
@@ -66,6 +66,12 @@
 #define	CTR_ILINE_MASK		(0xf << CTR_ILINE_SHIFT)
 #define	CTR_ILINE_SIZE(reg)	(((reg) & CTR_ILINE_MASK) >> CTR_ILINE_SHIFT)
 
+/* DCZID_EL0 - Data Cache Zero ID register */
+#define DCZID_DZP		(1 << 4) /* DC ZVA prohibited if non-0 */
+#define DCZID_BS_SHIFT		0
+#define DCZID_BS_MASK		(0xf << DCZID_BS_SHIFT)
+#define	DCZID_BS_SIZE(reg)	(((reg) & DCZID_BS_MASK) >> DCZID_BS_SHIFT)
+
 /* ESR_ELx */
 #define	ESR_ELx_ISS_MASK	0x00ffffff
 #define	 ISS_INSN_FnV		(0x01 << 10)
Index: head/sys/conf/files.arm64
===================================================================
--- head/sys/conf/files.arm64
+++ head/sys/conf/files.arm64
@@ -12,6 +12,7 @@
 arm64/arm64/bus_space_asm.S	standard
 arm64/arm64/busdma_bounce.c	standard
 arm64/arm64/busdma_machdep.c	standard
+arm64/arm64/bzero.S		standard
 arm64/arm64/clock.c		standard
 arm64/arm64/copyinout.S		standard
 arm64/arm64/copystr.c		standard