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Keir Fraser
b3bc7b059a
Add a couple of documentation details about PV-GRUB support - the menu.lst content can be passed as a ramdisk. - virtual partitions are not supported. Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
102 lines
2.5 KiB
Plaintext
102 lines
2.5 KiB
Plaintext
IOEMU stubdom
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=============
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This boosts HVM performance by putting ioemu in its own lightweight domain.
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General Configuration
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=====================
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Due to a race between the creation of the IOEMU stubdomain itself and allocation
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of video memory for the HVM domain, you need to avoid the need for ballooning,
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by using the hypervisor dom0_mem= option for instance.
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There is a sample configuration set in xmexample.hvm-stubdom
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In your HVM config "hvmconfig" use stubdom-dm as dm script:
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device_model = 'stubdom-dm'
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To run
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======
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mkdir -p /exports/usr/share/xen/qemu
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ln -s /usr/share/xen/qemu/keymaps /exports/usr/share/xen/qemu
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mkdir -p /exports/var/lib
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ln -s /var/lib/xen /exports/var/lib
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/usr/sbin/fs-backend &
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xm create hvmconfig
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PV-GRUB
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=======
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This replaces pygrub to boot domU images safely: it runs the regular grub
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inside the created domain itself and uses regular domU facilities to read the
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disk / fetch files from network etc. ; it eventually loads the PV kernel and
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chain-boots it.
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Configuration
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=============
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In your PV config,
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- use pv-grub.gz as kernel:
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kernel = "pv-grub.gz"
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- set the path to menu.lst, as seen from the domU, in extra:
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extra = "(hd0,0)/boot/grub/menu.lst"
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or you can provide the content of a menu.lst stored in dom0 by passing it as a
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ramdisk:
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ramdisk = "/boot/domU-1-menu.lst"
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or you can also use a tftp path (dhcp will be automatically performed):
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extra = "(nd)/somepath/menu.lst"
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or you can set it in option 150 of your dhcp server and leave extra and ramdisk
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empty (dhcp will be automatically performed)
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Limitations
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===========
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- You can not boot a 64bit kernel with a 32bit-compiled PV-GRUB and vice-versa.
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To cross-compile a 32bit PV-GRUB,
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export XEN_TARGET_ARCH=x86_32
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- bootsplash is supported, but the ioemu backend does not yet support restart
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for use by the booted kernel.
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- PV-GRUB doesn't support virtualized partitions. For instance:
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disk = [ 'phy:hda7,hda7,w' ]
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will be seen by PV-GRUB as (hd0), not (hd0,6), since GRUB will not see any
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partition table.
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Your own stubdom
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================
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By running
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cd stubdom/
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make c-stubdom
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or
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cd stubdom/
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make caml-stubdom
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you can compile examples of C or caml stub domain kernels. You can use these
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and the relevant Makefile rules as basis to build your own stub domain kernel.
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Available libraries are libc, libxc, libxs, zlib and libpci.
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