memory/gmap: add test for shadow memory counters

KVM records shadow memory events for a nested guest.
Confirm the counters go up.

Signed-off-by: Sebastian Mitterle <[email protected]>

libvirt/tests/cfg/memory/gmap.cfg

@@ -0,0 +1,7 @@
+- gmap:
+    type = gmap
+    start_vm = no
+    only s390-virtio
+    variants:
+        - l3_shadow_table_counters:
+            l2_mem = 3906250

libvirt/tests/src/memory/gmap.py

@@ -0,0 +1,139 @@
+import logging as log
+import os
+from pathlib import Path
+
+from avocado.core.exceptions import TestError
+from virttest import virsh
+from virttest.libvirt_xml import vm_xml
+from virttest.utils_misc import cmd_status_output
+from virttest.utils_test.libvirt_device_utils import create_fs_xml
+
+
+logging = log.getLogger('avocado.' + __name__)
+cleanup_actions = []
+
+
+def parent(file_path):
+    """
+    Returns the parent directory of a file path
+
+    :param file_path: absolute file path
+    :return path: absolute path of parent directory
+    """
+    return Path(file_path).parent.absolute()
+
+
+def get_source_disk_path(vmxml):
+    """
+    Returns the absolute path to a disk image for import.
+    Assume the boot image is the first disk and an image file.
+
+    :param vmxml: VMXML instance
+    :return: absolute path to the guest's first disk image file
+    """
+    disks = vmxml.get_disk_all()
+    disk_list = list(disks.values())
+    first_disk = disk_list[0]
+    return first_disk.find('source').get('file')
+
+
+def update_l2_vm(vmxml, l2_mem, target_tag):
+    """
+    Update the L2 VM to run L3 inside from virtiofs
+
+    :param vmxml: The VMXML instance
+    :param l2_mem: The new memory size
+    :param target_tag: virtiofs mount tag
+    """
+    vmxml.memory = l2_mem
+    mb = vm_xml.VMMemBackingXML()
+    mb.access_mode = "shared"
+    vmxml.mb = mb
+    vmxml.sync()
+    fs = create_fs_xml({
+        "accessmode": "passthrough",
+        "source": {
+            "dir": parent(get_source_disk_path(vmxml))
+            },
+        "target": {"dir": target_tag},
+        "binary": {"flock": "off", "posix": "off"}
+        })
+    virsh.attach_device(vmxml.vm_name, fs.xml, flagstr="--config", debug=True)
+
+
+def prepare_l3(vmxml):
+    """
+    Prepares the disk for the L3 guest
+
+    :param vmxml: The L2 VMXML instance
+    """
+    l2_disk_path = get_source_disk_path(vmxml)
+    l3_disk_path = os.path.join(parent(l2_disk_path), "test.qcow2")
+    cmd = ("qemu-img convert -f qcow2 -O qcow2 -o lazy_refcounts=on"
+           " {} {}".format(l2_disk_path, l3_disk_path))
+    cmd_status_output(cmd)
+    cleanup_actions.append(lambda: os.unlink(l3_disk_path))
+
+
+def start_l3(session, target_tag):
+    """
+    Mount the shared directory with the image file and start
+    the L3 guest with the qemu-kvm command
+
+    :param session: VM session
+    :param target_tag: virtiofs mount tag
+    """
+    mount_dir = "/mnt"
+    cmd = "mount -t virtiofs {} {}".format(target_tag, mount_dir)
+    cmd_status_output(cmd, session=session)
+    cmd = ("/usr/libexec/qemu-kvm -m 1024 -smp 1"
+           " -daemonize {}".format(os.path.join(mount_dir, "test.qcow2")))
+    s, _ = cmd_status_output(cmd, session=session)
+    if s:
+        raise TestError("Couldn't start L3 guest.")
+
+
+def l1_counters_go_up():
+    """
+    Check that the shadow memory counters go up
+    """
+    base_path = "/sys/kernel/debug/kvm/"
+    for a in [
+            "gmap_shadow_reuse",
+            "gmap_shadow_create",
+            "gmap_shadow_sg_entry",
+            "gmap_shadow_pg_entry"
+            ]:
+        with open(os.path.join(base_path, a), "r") as f:
+            if f.read().strip() == "0":
+                return False
+    return True
+
+
+def run(test, params, env):
+    """
+    Test kvm counters for L3 shadow memory
+    """
+    vm_name = params.get('main_vm')
+    vmxml = vm_xml.VMXML.new_from_inactive_dumpxml(vm_name)
+    bkxml = vmxml.copy()
+    cleanup_actions.append(lambda: bkxml.sync())
+    vm = env.get_vm(vm_name)
+    l2_mem = int(params.get("l2_mem", "4096"))
+    target_tag = "mnt"
+
+    try:
+        update_l2_vm(vmxml, l2_mem, target_tag)
+        prepare_l3(vmxml)
+        logging.debug("VMXML: %s", vm_xml.VMXML.new_from_dumpxml(vm_name))
+        vm.start()
+        cleanup_actions.append(lambda: vm.destroy())
+        session = vm.wait_for_login()
+        cleanup_actions.append(lambda: session.close())
+        start_l3(session, target_tag)
+        if not l1_counters_go_up():
+            test.fail("Gmap counters didn't go up.")
+    finally:
+        cleanup_actions.reverse()
+        for a in cleanup_actions:
+            a()