HEADS UP: Imported Xen 4.7 and blkback changes

[Roger Pau Monné]

Hello,

First of all, this message is only relevant to those that use FreeBSD as 
Dom0 (host), not as a DomU (guest), so don't panic.

I've imported the latest Xen version (4.7-rc4) into the ports tree, it's 
still not the final version, but it's quite close, so we better start 
testing it to make sure it works fine with FreeBSD.

One of the more relevant changes in 4.7 regarding FreeBSD is the support for 
block hotplug scripts. This means that we now have the option to use 
backends different than simple block or regular files, provided that someone 
writes the proper hotplug scripts to attach them (I've heard there are some 
iSCSI hotplug scripts around). This however requires changes in blkback, so 
if you plan to use the Xen 4.7 port, please make sure that you are running a 
kernel that contains revision r301269 (or any later version). The same also 
works the other way around, if you update your kernel past r301269, you will 
have to run Xen 4.7 or else disks are not going to work.

Also, and depending on your hardware, you will also need to add 
hw.pci.mcfg=0 to your /boot/loader.conf file after updating to Xen 4.7.

Roger.