test: add integration test for physical counter reset

Add a test to verify the reset of the physical counter on aarch64 VMs.
To do this we check registers saved in the snapshot and verify
the counter value is less than some reasonably small number we choose.
The value is based on the observation of how much cycles it takes for
a VM to boot and be snapshotted. The idea is that this value will always
be smaller than the actual physical counter on the host.

Signed-off-by: Egor Lazarchuk <yegorlz@amazon.co.uk>

Author: ShadowCurse

tests/integration_tests/functional/test_snapshot_basic.py

@@ -5,15 +5,19 @@
 import filecmp
 import logging
 import os
+import platform
 import re
 import shutil
 import time
 from pathlib import Path
 
 import pytest
 
+import host_tools.cargo_build as host
 import host_tools.drive as drive_tools
+from framework import utils
 from framework.microvm import SnapshotType
+from framework.properties import global_props
 from framework.utils import check_filesystem, check_output
 from framework.utils_vsock import (
     ECHO_SERVER_PORT,
@@ -540,3 +544,56 @@ def test_vmgenid(guest_kernel_linux_6_1, rootfs, microvm_factory, snapshot_type)
 
         # Update the base for next iteration
         base_snapshot = snapshot
+
+
+# TODO add `global_props.host_os == "amzn2"` condition
+# once amazon linux kernels have patches.
+@pytest.mark.skipif(
+    platform.machine() != "aarch64" or global_props.host_linux_version_tpl < (6, 4),
+    reason="This is aarch64 specific test and should only be run on 6.4 and later kernels",
+)
+def test_physical_couter_reset_aarch64(uvm_nano):
+    """
+    Test that the CNTPCT_EL0 register is reset on VM boot.
+    We assume the smallest VM will not consume more than
+    some MAX_VALUE cycles to be created and snapshotted.
+    The MAX_VALUE is selected by doing a manual run of this test and
+    seeing what the actual counter value is. The assumption here is that
+    if resetting will not occur the guest counter value will be huge as it
+    will be a copy of host value. The host value in its turn will be huge because
+    it will include host OS boot + CI prep + other CI tests ...
+    """
+    vm = uvm_nano
+    vm.add_net_iface()
+    vm.start()
+
+    snapshot = vm.snapshot_full()
+    vm.kill()
+    snap_editor = host.get_binary("snapshot-editor")
+
+    cntpct_el0 = hex(0x603000000013DF01)
+    # If a CPU runs at 3GHz, it will have a counter value of 1_000_000_000
+    # in 1/3 of a second. The host surely will run for more than 1/3 second before
+    # executing this test.
+    max_value = 800_000_000
+
+    cmd = [
+        str(snap_editor),
+        "info-vmstate",
+        "vcpu-states",
+        "--vmstate-path",
+        str(snapshot.vmstate),
+    ]
+    _, stdout, _ = utils.check_output(cmd)
+
+    # The output will look like this:
+    # kvm_mp_state: 0x0
+    # mpidr: 0x80000000
+    # 0x6030000000100000 0x0000000e0
+    # 0x6030000000100002 0xffff00fe33c0
+    for line in stdout.splitlines():
+        parts = line.split()
+        if len(parts) == 2:
+            reg_id, reg_value = parts
+            if reg_id == cntpct_el0:
+                assert int(reg_value, 16) < max_value