Features/XenPvopsDom0

Feature Name

Summary

Dom0 support for pvops-based kernel-xen .

Owner

• Name: EduardoHabkost, MarkMcLoughlin

Others involved: Stephen Tweedie, Chris Wright, Juan Quintela, Markus Armbruster, Glauber Costa, DanielBerrange, ...

Current status

• Targeted release: Unknown
• Upsteam status: http://wiki.xensource.com/xenwiki/XenParavirtOps
• Latest pv_ops dom0 patches: http://xenbits.xen.org/paravirt_ops/patches.hg/
• Last updated: 2008-07-30
• Percentage of completion: 30%

Fedora 10 shipped with Xen i686 and x86_64 DomU support enabled in the stock kernel - i.e. there is no more kernel-xen. Tracker bug for Fedora 10 Xen kernel work : [1]

i386 Dom0

• Not yet in rawhide kernel-xen
• Boots, though bare metal is now non-functional until hacks are cleaned up
• DMA (and thus real hardware drivers) working (if it doesn't straddle page boundaries)
• Core needs major cleanup
• Status at http://lists.xensource.com/archives/html/xen-devel/2008-02/msg00047.html
• http://lists.xensource.com/archives/html/xen-devel/2008-02/msg00242.html
• No backend drivers yet
• Conflicts with x86_64 DomU patches

Detailed Description

See Features/XenPvops for a rationale. This feature just continues to paravirt_ops Xen effort to bring it back to feature parity with Fedora 8 Xen.

Scope

Work items:

• Clean up and finish Dom0 boot patches (StephenTweedie, JuanQuintela, MarkMcLoughlin)
  • Backend drivers blkback/blktap and netback requiring: (StephenTweedie, JuanQuintela, MarkMcLoughlin)
  • Some ballooning bits
  • Foreign pages (i.e. PAGE_FOREIGN and VM_FOREIGN)
  • zap_pte()
  • Grant table ops
  • Save / restore
  • Memory ballooning
• x86_64: (DONE)
  • Latest x86.git has useful patches on paravirt_ops pagetable handling
  • ia32 emulation support
  • SMP support
  • Debug other problems that may appear
  • Cleanup of code for inclusion upstream
  • Some code need to be changed to be enabled at runtime if running under xen, instead of being enabled at compile time (pvops infra-structure may need to be extended to make it possible, on some cases)

Merged kernel: (DONE)

• Merge kernel-xen into 'kernel' RPM (MarkMcLoughlin)
• Make bzImage bootable so the same kernel can boot on Xen and bare-metal
  • Patches for DomU bzImage boot are in xen-unstable and x86.git
  • Adding Dom0 bzImage boot to the HV is a bit harder
• Remove images/xen/{initrd,vmlinux} from install trees (JeremyKatz ?)
• Make 'new-kernel-pkg' aware of HYPERVISOR setting in /etc/sysconfig/xen (DanielBerrange)
• Make virt-install use images/pxeboot/{initrd,vmlinux} for DomU installs (DanielBerrange)
• Make 'xen' SRPM build a xen-hypervisor containing the HV (DanielBerrange)

Nice to have:

• CPU hotplug
• Migration support
• 32-on-64 support (both DomU and Dom0)
• LiveCD with pvops enabled kernel as DomU ?
• Kexec on pvops dom0

Unlikely to get: (ie feature regressions)

• PCI device passthrough to DomU

Finished items:

• x86_64 support upstream (see above)
• Merged kernel (see above)
• First-cut of Dom0 boot (StephenTweedie, JuanQuintela, MarkMcLoughlin)
• ACPI
• ioremap
• IRQ routing
• DMA/contiguous pages
• MTRR
• privcmd interface, other /proc/xen bits, /sys/hypervisor, /dev/evtchn (MarkMcLoughlin)

Test Plan

• Install a Fedora 10 host/Dom0 system
• Turn on Xen Hypervisor by setting 'HYPERVISOR=/boot/xen-3.2.gz' in /etc/sysconfig/kernel and running some tool (TBD)
• Turn on Xen Userspace by running 'chkconfig xend on'
• Reboot
• Observe presence of Xen via /sys/hypervisor/
• Run 'xm list' and observe Domain-0
• Use virt-install to deploy a Fedora 9/10 paravirt guest
• Use virt-install to deploy a Fedora 8 paravirt guest
• Use virt-install to deploy a Fedora 8 fullyvirt guest
• Use 'virsh' to save & restore a PV guest and HVM guest
• Balloon down memory of a guest with virsh.

User Experience

• Xen-ified kernel has same version as bare metal kernel
• All kernel updates support Xen
• All hardware that works in baremetal works in Xen Dom0
• No separate kernel RPM required for Xen DomU or Dom0
• Can enable/disable use of HV via a /etc/sysconfig setting

Dependencies

• Update to anaconda to not build a 'images/xen/' directory anymore
• Update to 'new-kernel-pkg' to know how to install HV

Contingency Plan

If Dom0 support is still not ready for Fedora 10 GA, the options are:

• Continue to ship with only DomU support
• Drop Xen support altogether