fix: boottimer device MMIO address

When we re-arranged the MMIO address space in commit 9a165d1 (arch:
define 64-bit capable MMIO memory regions) we moved the MMIO region of
the boot timer device for x86 systems, but we didn't update the init
scripts that hardcode it and use it to report boot time timestamp back
to Firecracker.

Update the init.c and initramfs values for the region. Also, add a
functional test that runs during CI PR tests and makes sure the boot
timer works.

Signed-off-by: Babis Chalios <bchalios@amazon.es>

Author: bchalios

resources/overlay/usr/local/bin/init.c

@@ -13,7 +13,7 @@
 // Position on the bus is defined by MMIO_LEN increments, where MMIO_LEN is
 // defined as 0x1000 in vmm/src/device_manager/mmio.rs.
 #ifdef __x86_64__
-#define MAGIC_MMIO_SIGNAL_GUEST_BOOT_COMPLETE 0xd0000000
+#define MAGIC_MMIO_SIGNAL_GUEST_BOOT_COMPLETE 0xc0000000
 #endif
 #ifdef __aarch64__
 #define MAGIC_MMIO_SIGNAL_GUEST_BOOT_COMPLETE 0x40000000

resources/rebuild.sh

@@ -92,7 +92,7 @@ function build_initramfs {
 
     # Report guest boot time back to Firecracker via MMIO
     # See arch/src/lib.rs and the BootTimer device
-    MAGIC_BOOT_ADDRESS=0xd0000000
+    MAGIC_BOOT_ADDRESS=0xc0000000
     if [ $ARCH = "aarch64" ]; then
         MAGIC_BOOT_ADDRESS=0x40000000
     fi

tests/integration_tests/performance/test_boottime.py

@@ -94,6 +94,33 @@ def to_ms(v, unit):
     return kernel, userspace, total
 
 
+def launch_vm_with_boot_timer(
+    microvm_factory, guest_kernel_acpi, rootfs_rw, vcpu_count, mem_size_mib
+):
+    """Launches a microVM with guest-timer and returns the reported metrics for it"""
+    vm = microvm_factory.build(guest_kernel_acpi, rootfs_rw)
+    vm.jailer.extra_args.update({"boot-timer": None})
+    vm.spawn()
+    vm.basic_config(
+        vcpu_count=vcpu_count,
+        mem_size_mib=mem_size_mib,
+        boot_args=DEFAULT_BOOT_ARGS + " init=/usr/local/bin/init",
+        enable_entropy_device=True,
+    )
+    vm.add_net_iface()
+    vm.start()
+    vm.pin_threads(0)
+
+    boot_time_us, cpu_boot_time_us = get_boottime_device_info(vm)
+
+    return (vm, boot_time_us, cpu_boot_time_us)
+
+
+def test_boot_timer(microvm_factory, guest_kernel_acpi, rootfs):
+    """Tests that the boot timer device works"""
+    launch_vm_with_boot_timer(microvm_factory, guest_kernel_acpi, rootfs, 1, 128)
+
+
 @pytest.mark.parametrize(
     "vcpu_count,mem_size_mib",
     [(1, 128), (1, 1024), (2, 2048), (4, 4096)],
@@ -105,20 +132,9 @@ def test_boottime(
     """Test boot time with different guest configurations"""
 
     for i in range(10):
-        vm = microvm_factory.build(guest_kernel_acpi, rootfs_rw)
-        vm.jailer.extra_args.update({"boot-timer": None})
-        vm.spawn()
-        vm.basic_config(
-            vcpu_count=vcpu_count,
-            mem_size_mib=mem_size_mib,
-            boot_args=DEFAULT_BOOT_ARGS + " init=/usr/local/bin/init",
-            enable_entropy_device=True,
+        vm, boot_time_us, cpu_boot_time_us = launch_vm_with_boot_timer(
+            microvm_factory, guest_kernel_acpi, rootfs_rw, vcpu_count, mem_size_mib
         )
-        vm.add_net_iface()
-        vm.start()
-        vm.pin_threads(0)
-
-        boot_time_us, cpu_boot_time_us = get_boottime_device_info(vm)
 
         if i == 0:
             metrics.set_dimensions(