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https://github.com/retspen/webvirtcloud
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feat(instances): a shut-off UEFI VM can be migrated
The move copies the VM's NVRAM file to the destination with libvirt streams (unless both hosts share the NVRAM directory) and removes the copy if the move fails; the source's file goes with the existing cleanup. The undefine keeps the file, as libvirt refuses to undefine a VM with NVRAM otherwise. A VM with TPM state is still refused.
This commit is contained in:
catborise
parent
6e53b07475
commit
d3e4ef9132
6 changed files with 191 additions and 60 deletions
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@ -1,4 +1,5 @@
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import contextlib
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import io
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import ipaddress
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import json
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import logging
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@ -18,6 +19,7 @@ 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_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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@ -158,30 +160,65 @@ class wvmInstances(wvmConnect):
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# Once supported hosts all run a fixed libvirt, this branch and
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# move_definition can go: the flags above are those for
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# dom.migrate.
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self.move_definition(dom)
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self.move_definition(dom, conn)
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else:
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dom.migrate(self.wvm, flags, None, uri, 0)
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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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"""A shut-off VM moves without its TPM state, a file of the source
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host: on the destination it would get a new TPM that no longer
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unlocks its disks. A live migration carries it. (The UEFI variables
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are copied: copy_nvram.)"""
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if ElementTree.fromstring(xml).find("devices/tpm/backend[@type='emulator']") is not None:
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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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"A shut-off VM with TPM state cannot be migrated: the state stays on the source host. "
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"Start the VM and migrate it live."
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)
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def copy_nvram(self, conn):
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"""Copies the UEFI variables file of the shut-off VM of conn (on the
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source) from libvirt's NVRAM directory there to the same path here,
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unless both hosts share that directory. Returns the copy's name."""
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path = conn.get_nvram()
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if not path or os.path.dirname(path) != NVRAM_DIR:
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return None
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name = os.path.basename(path)
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with conn._nvram_pool() as source, self._nvram_pool() as target:
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vol = self._find_volume(source, name)
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if vol is None:
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return None # never started: libvirt creates it at the first start
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if self._nvram_shared(source, target):
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if self._find_volume(target, name) is None:
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raise util.OperationError(f"The destination host cannot see the NVRAM file {path}")
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return None
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chunks = []
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stream = conn.wvm.newStream(0)
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vol.download(stream, 0, 0, 0)
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stream.recvAll(lambda _stream, data, out: out.append(data), chunks)
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stream.finish()
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data = b"".join(chunks)
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copy = target.createXML(
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f"<volume><name>{util.xml_escape(name)}</name><capacity>{len(data)}</capacity>"
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"<target><format type='raw'/></target></volume>",
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0,
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)
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try:
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stream = self.wvm.newStream(0)
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copy.upload(stream, 0, len(data), 0)
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stream.sendAll(lambda _stream, size, buffer: buffer.read(size), io.BytesIO(data))
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stream.finish()
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except Exception:
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copy.delete(0)
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raise
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return name
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def delete_nvram(self, name):
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if name:
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with self._nvram_pool() as pool:
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pool.storageVolLookupByName(name).delete(0)
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def missing_disks(self, definitions):
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"""(target, source) of the disks in the VM definitions (XML) that are
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not volumes of this host's active storage pools: the VM's own files,
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@ -252,10 +289,11 @@ class wvmInstances(wvmConnect):
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return None
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raise
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def move_definition(self, dom):
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def move_definition(self, dom, conn):
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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 (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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are on storage both hosts share, and its UEFI variables file
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(copy_nvram; moveto refuses a VM with TPM state). The destination's
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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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@ -278,9 +316,15 @@ class wvmInstances(wvmConnect):
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xml = dom.XMLDesc(VIR_DOMAIN_XML_SECURE | VIR_DOMAIN_XML_MIGRATABLE)
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autostart = dom.autostart()
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new = self.wvm.defineXML(xml)
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nvram = self.copy_nvram(conn)
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try:
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dom.undefineFlags(0)
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new = self.wvm.defineXML(xml)
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except Exception:
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self.delete_nvram(nvram)
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raise
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try:
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# libvirt refuses to undefine a VM with NVRAM without this; the file stays for the cleanup
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dom.undefineFlags(VIR_DOMAIN_UNDEFINE_KEEP_NVRAM)
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try:
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started = dom.isActive()
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except libvirtError as error:
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@ -292,7 +336,8 @@ 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, error)
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self.undo_definition(dom, new, error) # raises when the destination keeps the VM
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self.delete_nvram(nvram)
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raise
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@staticmethod
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@ -308,7 +353,7 @@ 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(0)
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new.undefineFlags(VIR_DOMAIN_UNDEFINE_KEEP_NVRAM)
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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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@ -447,7 +492,8 @@ class wvmInstance(wvmConnect):
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return util.get_xml_path(self._XMLDesc(0), "/domain/devices/emulator")
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def get_nvram(self):
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return util.get_xml_path(self._XMLDesc(0), "/domain/os/nvram")
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xml = self._XMLDesc(0) # a path as text, or a <source file=...> since libvirt 8.5
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return util.get_xml_path(xml, "/domain/os/nvram/source/@file") or util.get_xml_path(xml, "/domain/os/nvram")
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def get_loader(self):
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xml = self._XMLDesc(0)
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