Live-Updating Xen

Live-Updating Xen

Current State

• kexec work merged for v2.0.20
• PV domU serialization work ongoing

Initial proof-of-concept with patches from Varad's tree (link below) - no kexec involved:

Save a PV domain state, leave guest memory in the RAM:
# xl save -s domU domU.img 

Restore domain state reusing magic mfns. The shared_info page contents are preserved:
# xl restore -T domU.img <l3tab_mfn> <l2tab_mfn> <shared_info_mfn>

TODO: Restore console, reconstruct guest pagetables from shared_info.

Development trees

http://git.infradead.org/users/dwmw2/xen.git/shortlog/refs/heads/bootcleanup

https://github.com/varadgautam/xen/tree/liveupdate-devel

TODO

This list will move to the JIRA instance

• Devel milestone: PV domU persists across domain destroy/create
• Dom0 persists across kexec
• HVM guests persist across kexec
• PV guests persist across kexec
• One guest persists across kexec
• Multiple guests persist across kexec
• Guests exercise workloads
• Update to same Xen binary as the Target Xen
• Update to a Xen binary with a minor change, like a new printk
• Update to a Xen binary with a fix for an XSA
• Update to a new minor version
• Update to a new major version

More information

• Slides from Xen Summit 2019
• Video recording of the Xen Summit 2019 talk