[arch][arm] conditionalize the code to boot the secondary cpus in arch_init()

On some platforms, the secondary cpus have been booted and trapped by the arch/arm code
and need to be brought up lockstep to make sure the temporary page mappings are
still in place as they are booted. For these platforms, set
ARM_ARCH_BOOTS_SECONDARIES=1 to have arch_init() try to release and start the cpus.

For other platforms, after arch_init() they can simply arrange for the secondary cpus
to start themselves.

Change-Id: I7619ac66d84bd26060ddd949ae6641c1ef6e2b1d

arch/arm/arm/arch.c

@@ -128,6 +128,11 @@ void arch_init(void)
 
 	lk_init_secondary_cpus(secondaries_to_init);
 
+#if ARM_ARCH_BOOTS_SECONDARIES
+	/* in platforms where the cpus have already been started, go ahead and wake up all the
+	 * secondary cpus here.
+	 * TODO: find a cleaner way to do this than this #define
+	 */
 	dprintf(SPEW, "releasing %d secondary cpu%c\n", secondaries_to_init, secondaries_to_init > 1 ? 's' : ' ');
 
 	/* release the secondary cpus */
@@ -135,7 +140,15 @@ void arch_init(void)
 
 	/* flush the release of the lock, since the secondary cpus are running without cache on */
 	arch_clean_cache_range((addr_t)&arm_boot_cpu_lock, sizeof(arm_boot_cpu_lock));
+
+	/* wait for secondary cpus to boot before arm_mmu_init below, which will remove
+	 * temporary boot mappings
+	 */
+	while (secondaries_to_init > 0) {
+		__asm__ volatile("wfe");
+	}
 #endif
+#endif // WITH_SMP
 
 	//spinlock_test();
 

platform/bcm2835/rules.mk

@@ -37,7 +37,8 @@ KERNEL_BASE = 0x80000000
 
 GLOBAL_DEFINES += \
 	MEMBASE=$(MEMBASE) \
-	MEMSIZE=$(MEMSIZE)
+	MEMSIZE=$(MEMSIZE) \
+	ARM_ARCH_BOOTS_SECONDARIES=1
 
 LINKER_SCRIPT += \
 	$(BUILDDIR)/system-onesegment.ld

platform/vexpress-a9/rules.mk

@@ -26,7 +26,8 @@ MODULE_DEPS += \
 
 GLOBAL_DEFINES += \
 	MEMBASE=$(MEMBASE) \
-	MEMSIZE=$(MEMSIZE)
+	MEMSIZE=$(MEMSIZE) \
+	ARM_ARCH_BOOTS_SECONDARIES=1
 
 LINKER_SCRIPT += \
 	$(BUILDDIR)/system-onesegment.ld

platform/zynq/rules.mk

@@ -42,7 +42,8 @@ MODULE_SRCS += \
 	$(LOCAL_DIR)/gem.c \
 
 GLOBAL_DEFINES += \
-	ZYNQ_WITH_GEM_ETH=1
+	ZYNQ_WITH_GEM_ETH=1 \
+	ARM_ARCH_BOOTS_SECONDARIES=1
 
 # gem driver depends on minip interface
 MODULE_DEPS += \