Enable SMP on the qemu virt platform. We use the device tree to find which

cpus to enable, and PSCI to start them.

sys/arm/conf/VIRT

@@ -24,8 +24,9 @@ include 	"std.armv6"
 include 	"../qemu/std.virt"
 
 options 	HZ=100
-options 	SCHED_4BSD		# 4BSD scheduler
+options 	SCHED_ULE		# 4BSD scheduler
 options 	PLATFORM
+options 	SMP			# Enable multiple cores
 
 # Debugging for use in -current
 makeoptions	DEBUG=-g		# Build kernel with gdb(1) debug symbols

sys/arm/qemu/files.qemu

@@ -13,5 +13,6 @@ kern/kern_clocksource.c			standard
 arm/arm/generic_timer.c			standard
 arm/qemu/virt_common.c			standard
 arm/qemu/virt_machdep.c			standard
+arm/qemu/virt_mp.c			optional	smp
 
 dev/ofw/ofw_cpu.c			standard

sys/arm/qemu/virt_mp.c

@@ -0,0 +1,119 @@
+/*-
+ * Copyright (c) 2015 Andrew Turner
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <sys/param.h>
+#include <sys/systm.h>
+#include <sys/bus.h>
+#include <sys/pcpu.h>
+#include <sys/smp.h>
+
+#include <vm/vm.h>
+#include <vm/pmap.h>
+
+#include <machine/intr.h>
+#include <machine/smp.h>
+
+#include <dev/ofw/openfirm.h>
+#include <dev/ofw/ofw_cpu.h>
+#include <dev/psci/psci.h>
+
+static int running_cpus;
+
+int
+platform_mp_probe(void)
+{
+	int ncpus;
+
+	ncpus = ofw_cpu_early_foreach(NULL, true);
+	if (ncpus <= 1) {
+		mp_ncpus = 1;
+		return (0);
+	}
+
+	mp_ncpus = MIN(ncpus, MAXCPU);
+
+	return (1);
+}
+
+static boolean_t
+virt_maxid(u_int id, phandle_t node, u_int addr_cells, pcell_t *reg)
+{
+
+	if (mp_maxid < id)
+		mp_maxid = id;
+
+	return (true);
+}
+
+void
+platform_mp_setmaxid(void)
+{
+
+	mp_maxid = PCPU_GET(cpuid);
+	ofw_cpu_early_foreach(virt_maxid, true);
+}
+
+static boolean_t
+virt_start_ap(u_int id, phandle_t node, u_int addr_cells, pcell_t *reg)
+{
+	int err;
+
+	if (running_cpus >= mp_ncpus)
+		return (false);
+	running_cpus++;
+
+	err = psci_cpu_on(*reg, pmap_kextract((vm_offset_t)mpentry), id);
+
+	if (err != PSCI_RETVAL_SUCCESS)
+		return (false);
+
+	return (true);
+}
+
+void
+platform_mp_start_ap(void)
+{
+
+	ofw_cpu_early_foreach(virt_start_ap, true);
+}
+
+void
+platform_mp_init_secondary(void)
+{
+
+	arm_init_secondary_ic();
+}
+
+void
+platform_ipi_send(cpuset_t cpus, u_int ipi)
+{
+
+	pic_ipi_send(cpus, ipi);
+}