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Re: [Publicity] Xen 4.4 features for press release

George, (+Stefano)
thank you. This looks like a great start. I am wondering whether for Xen on ARM 
we should list the HW platforms against which Xen 4.4 was validated against. 
Also, I am wondering whether we should xref to some non-server use-cases (one 
for Stefano - need to think about this a bit more). 
P.S.: I will get approval for the 4.4 press release from the Advisory Board 

-----Original Message-----
From: George Dunlap [mailto:george.dunlap@xxxxxxxxxxxxx] 
Sent: 16 December 2013 13:15
To: publicity@xxxxxxxxxxxxxxxxxxxx; Lars Kurth
Subject: Xen 4.4 features for press release

Below is the list of features in 4.4, explained as may be suitable for a press 
release.  Let me know if you have any corrections or improvements.


* Non-Linux driver domains.  One of Xen's unique features is that it is 
designed to run drivers inside of VMs, allowing better performance, security, 
and flexibility.  Until now, however, the core driver domain functionality 
required udev, which is only available in Linux.  This has been replaced with a 
daemon, allowing arbitrary OSes to be used as driver domains.

* Event channel scalability.  Event channels are per-VM resources that allow 
VMs to communicate with each other.  These were previously limited to eithe 
1024 or 4096 per domain.  Domain 0 needs several for each guest VM, so this 
limited the total number of VMs available to several hundred.  The new event 
channel implementation allows hundreds of thousands of event channels, removing 
this as a limit on the number of VMs which can be started.

* Experimental support for PVH mode for guests.  PVH mode combines the best 
elements of HVM and PV into a mode which allows Xen to take advantage of many 
of the hardware virtualization features without needing the overhead of 
simulating an entire physical computer. This will allow for increased 
efficiency, as well as reduced footprint in Linux going forward.

* Improved support for SPICE.  SPICE is a protocol for virtial desktops which 
allows a much richer connection than display-only protocols like VNC.  Xen 4.4 
adds support for additional functionality, including vdagent, clipboard 
sharing, and USB redirection.

* pvgrub2 (external).  Rather than have a custom implementation of grub for 
pvgrub, the upstream grub2 project now has a build target which will construct 
a bootable PV xen image.  This ensures 100% grub2 compatibility for pvgrub 
going forward.

* Indirect descriptors for block PV protocol (Linux).  Modern storage devices 
work much better with larger chunks of data.  Indirect descriptors have allowed 
the size of each individual request to triple, greatly improving performance 
when running on fast storage technologies like SSD and RAID.  This is available 
in any guest running Linux 3.11 or higher (regardless of Xen version).

* Improved kexec.  kexec functionality is primarily used when a crash happens, 
to allow a special kernel to come in afterwards and collect information about 
the cause of the crash, to allow developers to diagnose and fix the root cause.

* Improved xapi support.  xapi is a separate project written in OCaml, and 
relies on the Xen OCaml language bindings to operate well. These bindings have 
had a major overhaul, and should result in much better compatibility and 
support for distros going forward.

* Experimental support for Guest EFI boot.  EFI is the new booting standard 
that is replacing BIOS.  Some operating systems only boot with EFI; and some 
features, like SecureBoot, only work with EFI.

* 64-bit Xen on ARM now supports booting guests

* Updated to qemu 1.6 and SeaBIOS

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