IOEMU stubdom ============= This boosts HVM performance by putting ioemu in its own lightweight domain. General Configuration ===================== Due to a race between the creation of the IOEMU stubdomain itself and allocation of video memory for the HVM domain, you need to avoid the need for ballooning, by using the hypervisor dom0_mem= option for instance. Using with XL ------------- The enable IOEMU stub domains set the following in your domain config: device_model_stubdomain_override = 1 See xl.cfg(5) for more details of the xl domain configuration syntax and http://wiki.xen.org/wiki/Device_Model_Stub_Domains for more information on device model stub domains PV-GRUB ======= This replaces pygrub to boot domU images safely: it runs the regular grub inside the created domain itself and uses regular domU facilities to read the disk / fetch files from network etc. ; it eventually loads the PV kernel and chain-boots it. Configuration ============= In your PV config, - use pv-grub.gz as kernel: kernel = "pv-grub.gz" - set the path to menu.lst, as seen from the domU, in extra: extra = "(hd0,0)/boot/grub/menu.lst" or you can provide the content of a menu.lst stored in dom0 by passing it as a ramdisk: ramdisk = "/boot/domU-1-menu.lst" or you can also use a tftp path (dhcp will be automatically performed): extra = "(nd)/somepath/menu.lst" or you can set it in option 150 of your dhcp server and leave extra and ramdisk empty (dhcp will be automatically performed) Limitations =========== - You can not boot a 64bit kernel with a 32bit-compiled PV-GRUB and vice-versa. To cross-compile a 32bit PV-GRUB, export XEN_TARGET_ARCH=x86_32 - bootsplash is supported, but the ioemu backend does not yet support restart for use by the booted kernel. - PV-GRUB doesn't support virtualized partitions. For instance: disk = [ 'phy:hda7,hda7,w' ] will be seen by PV-GRUB as (hd0), not (hd0,6), since GRUB will not see any partition table. Your own stubdom ================ By running cd stubdom/ make c-stubdom or cd stubdom/ make caml-stubdom you can compile examples of C or caml stub domain kernels. You can use these and the relevant Makefile rules as basis to build your own stub domain kernel. Available libraries are libc, libxc, libxs, zlib and libpci.