Xen is being used in production by many folks, but are they really using the upstream code? If not what are they using? At least SUSE's supported delta for the Linux kernel consists of 116 patches totaling 353,770 lines of code. Debian has 43 patches for a delta of about 1693 lines of code. What is this delta and how do we shrink it? I will give an overview of the supported Linux kernel delta for Xen at SUSE and Debian with upstream but also layout a proposed roadmap of addressing the delta in collaboration with different teams in the Xen community.

1. Delta with Xen
on the Linux kernel
What’s up with all that delta?
@mcgrof
mcgrof@suse.com
Luis R. Rodriguez
http://www.do-not-panic.com
Slides: CC BY-SA Luis R. Rodriguez | Image: CC BY-SA Torkild Retvedt

2. How big is it?
Citrix: reset two years ago, mostly backports
Debian: 4 microcode patches
SUSE: the largest delta
SLE10: 133 patches
SLE11: 185 patches
SLE12: 110 patches
359,913 lines of code
git://gitorious.org/opensuse/kernel-source.git
patches.xen/
Image: CC BY-NC-SA ecololo

3. Addressing the delta
The xen wiki delta for Linux upstream tracker
Luis Rodriguez: IPv6 autoconf, netback
Juergen Gross: pvSCSI, PAT, 500GiB RAM
Daniel Kiper: EFI
Konrad Wilk: user mode pvlock
Boris Ostrovsky: oprofile support
● Attitude adjustment: work upstream first (™) Is it possible? Future
development always upstream
● Backport automatically
Image: CC BY-SA Teza Harinaivo Ramiandrisoa

4. Needs verification
pci-guestdev
mem-hotplug
hypercall preemption - patch posted, did it go in?
multipage ring
Image: CC BY-NC Sergiu Bacioiu

5. Needs work
● pvusb
● Expose ballooning limits
● Retaining tasklet in netback
● Add BLKIF_OP_PACKET, CDROM
command forwarding
● CDROM removable media attribute
● CDROM avoid takeover in HVM
● DCDBAS address translation
● Netback multicall for notifications
● Interrupt trigger mode and polarity
● Logarithmic scale for ballooning
● netfront support skb coalescing
● microcode update
● MTRR support
● Remove VM_IO vestiges
● Device hotplug (MODULE_ALIAS)
● Suspend event channel support for
faster checkpointing in Remus FT
● Expected to be dead code (under
xen) cannot easily be verified to be
dead
● Support for old hypervisor (pvops
kernel on xen pre-4.0.1 hypervisor)
● blktap driver (what about blktap3?)
Image: CC-BY m4tik