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https://github.com/retspen/webvirtcloud
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fix(vrtManager): a shut-off VM with NVRAM or TPM state is not migrated
libvirt keeps a VM's UEFI variables (NVRAM) and emulated TPM state in files of its host. A live migration carries both: on the test hosts (libvirt 11.10, QEMU 10.1) the destination got the same NVRAM content once the VM ran and the same TPM state, and the source TPM state was removed. Moving a shut-off VM moves only its definition, so neither went along: on its first start on the destination libvirt made a new NVRAM from the template and a new TPM. Boot entries and enrolled keys are lost, and disks sealed to the TPM no longer unlock. A shut-off VM whose definition has an NVRAM file or an emulated TPM is now refused before anything changes: "Start the VM and migrate it live." A passthrough or external TPM keeps no state on the host and still moves. The check sits in moveto, not in the define/undefine workaround, as libvirt's own offline migration does not carry the files either. The keep-NVRAM and keep-TPM undefine flags of that workaround are gone, as no VM that needs them reaches it. Checked on the test hosts: a shut-off UEFI VM with a TPM is refused and stays on the source with nothing defined on the destination; the same VM migrates live. The new tests fail on the previous code.
This commit is contained in:
catborise
parent
98bb6ebdb5
commit
c7a7c843fb
2 changed files with 49 additions and 19 deletions
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@ -18,8 +18,6 @@ try:
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VIR_DOMAIN_XML_SECURE,
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VIR_DOMAIN_XML_INACTIVE,
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VIR_DOMAIN_XML_MIGRATABLE,
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VIR_DOMAIN_UNDEFINE_KEEP_NVRAM,
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VIR_DOMAIN_UNDEFINE_KEEP_TPM,
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VIR_ERR_NO_DOMAIN,
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VIR_ERR_NO_STORAGE_POOL,
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VIR_ERR_NO_STORAGE_VOL,
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@ -156,6 +154,8 @@ class wvmInstances(wvmConnect):
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mode.append(label)
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dom = conn.instance
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if state == 5:
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self.refuse_local_state(dom.XMLDesc(0))
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definitions = {dom.XMLDesc(0)}
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if state != 5:
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definitions.add(dom.XMLDesc(VIR_DOMAIN_XML_INACTIVE))
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@ -184,6 +184,25 @@ class wvmInstances(wvmConnect):
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self.migrate_within(dom, flags, uri, timeout)
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return ", ".join(mode)
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@staticmethod
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def refuse_local_state(xml):
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"""A shut-off VM moves without its UEFI variables (NVRAM) and TPM
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state, which libvirt keeps in files of the source host: on the
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destination it would start with new ones (lost boot entries and
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enrolled keys, a new TPM that no longer unlocks disks). A live
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migration carries both."""
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tree = ElementTree.fromstring(xml)
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state = []
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if tree.find("os/nvram") is not None:
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state.append("NVRAM")
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if tree.find("devices/tpm/backend[@type='emulator']") is not None:
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state.append("TPM")
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if state:
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raise util.OperationError(
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f"A shut-off VM with {' and '.join(state)} state cannot be migrated: the state stays on the source "
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"host. Start the VM and migrate it live."
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)
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def migrate_within(self, dom, flags, uri, timeout):
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"""dom.migrate, cancelled when it has not finished after timeout
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seconds: a VM that changes its memory faster than the network carries
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@ -290,8 +309,8 @@ class wvmInstances(wvmConnect):
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def move_definition(self, dom):
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"""Migrates a shut-off VM: that is only its definition, as the disks
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are on storage both hosts share. NVRAM and TPM state stay on the
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source. The destination's qemu migration hook does not run for it.
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are on storage both hosts share (moveto refuses a VM with NVRAM or
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TPM state). The destination's qemu migration hook does not run for it.
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Workaround, to be removed in a later version: libvirt's own offline
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migration (VIR_MIGRATE_OFFLINE) fails with "operation failed: domain
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@ -315,13 +334,10 @@ class wvmInstances(wvmConnect):
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raise util.OperationError(f"The destination host already has a VM {key}")
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xml = dom.XMLDesc(VIR_DOMAIN_XML_SECURE | VIR_DOMAIN_XML_MIGRATABLE)
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keep = VIR_DOMAIN_UNDEFINE_KEEP_NVRAM
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if ElementTree.fromstring(xml).find("devices/tpm") is not None:
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keep |= VIR_DOMAIN_UNDEFINE_KEEP_TPM # libvirt >= 8.9 knows the flag
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autostart = dom.autostart()
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new = self.wvm.defineXML(xml)
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try:
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dom.undefineFlags(keep)
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dom.undefineFlags(0)
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try:
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started = dom.isActive()
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except libvirtError as error:
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@ -333,11 +349,11 @@ class wvmInstances(wvmConnect):
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dom.connect().defineXML(xml).setAutostart(autostart)
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raise util.OperationError("The VM was started on the source host during the migration")
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except Exception as error:
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self.undo_definition(dom, new, keep, error)
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self.undo_definition(dom, new, error)
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raise
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@staticmethod
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def undo_definition(dom, new, keep, error):
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def undo_definition(dom, new, error):
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"""After a failed move, the VM is defined on one host only: the
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destination definition goes only while the source still has its own."""
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try:
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@ -349,7 +365,7 @@ class wvmInstances(wvmConnect):
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f"{error}; the VM may now be defined only on the destination host: check both hosts"
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) from error
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try:
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new.undefineFlags(keep)
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new.undefineFlags(0)
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except libvirtError as undo_error:
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raise util.OperationError(
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f"{error}; the VM is now defined on both hosts, remove it from the destination: {undo_error}"
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@ -211,15 +211,29 @@ class ShutOffMigrationTestCase(unittest.TestCase):
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destination(host).moveto(source, "vm", live=False, unsafe=False, offline=True)
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self.assertEqual(host.defined, ["<domain><name>vm</name></domain>"])
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self.assertEqual(source.instance.calls, [])
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self.assertEqual(source.instance.undefined, libvirt.VIR_DOMAIN_UNDEFINE_KEEP_NVRAM)
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self.assertEqual(source.instance.undefined, 0)
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def test_tpm_state_stays_on_the_source(self):
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source = FakeSource(5, xml="<domain><devices><tpm model='tpm-crb'/></devices></domain>")
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destination().moveto(source, "vm", live=False, unsafe=False, offline=True)
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self.assertEqual(
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source.instance.undefined,
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libvirt.VIR_DOMAIN_UNDEFINE_KEEP_NVRAM | libvirt.VIR_DOMAIN_UNDEFINE_KEEP_TPM,
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)
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def test_a_vm_with_nvram_or_tpm_state_is_refused(self):
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"""That state stays on the source host: the VM would start on the
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destination with new UEFI variables and a new TPM."""
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cases = {
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"nvram": "<os><nvram>/var/lib/libvirt/qemu/nvram/vm_VARS.fd</nvram></os>",
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"tpm": "<devices><tpm model='tpm-crb'><backend type='emulator' version='2.0'/></tpm></devices>",
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}
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for case, xml in cases.items():
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with self.subTest(case=case):
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host = FakeHost()
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source = FakeSource(5, xml=f"<domain>{xml}</domain>")
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with self.assertRaisesRegex(util.OperationError, "migrate it live"):
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destination(host).moveto(source, "vm", live=False, unsafe=False, offline=True)
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self.assertEqual(host.defined, [])
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self.assertIsNone(source.instance.undefined)
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def test_a_tpm_without_local_state_moves(self):
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xml = "<domain><devices><tpm model='tpm-tis'><backend type='passthrough'/></tpm></devices></domain>"
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host = FakeHost()
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destination(host).moveto(FakeSource(5, xml=xml), "vm", live=False, unsafe=False, offline=True)
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self.assertEqual(host.defined, [xml])
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def test_refused_before_anything_changes(self):
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cases = {
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