Re: [Libvir] PATCH: Allow Xen HVM kernel+initrd booting
On Mon, Feb 04, 2008 at 09:44:12AM -0500, Daniel Veillard wrote:
So basically Xen PV, Xen FV and KVM <os> blocks should now share the
same set of functionalities, sharight the same syntax, right ? And the
refactoring comes from the 3 being able to share more code, if yes that
sounds excellent :-)
Almost the same. pv guests won't have use for a <boot dev="c"/> tag
since they have no BIOS, nor do they have a <loader> tag, but other
than that they're the same.
> <domain type='xen'>
> <name>kernel</name>
> <uuid>06ed00fe-1162-4fc4-b5d8-11993ee4a8b9</uuid>
> <os>
> <type>hvm</type>
> <loader>/usr/lib/xen/boot/hvmloader</loader>
> <kernel>/root/vmlinuz.f864</kernel>
> <initrd>/root/initrd.img.f864</initrd>
> <cmdline>console=ttyS0 console=tty0</cmdline>
> </os>
> <memory>540672</memory>
> <currentMemory>531456</currentMemory>
> <vcpu>1</vcpu>
> <on_poweroff>preserve</on_poweroff>
> <on_reboot>preserve</on_reboot>
> <on_crash>preserve</on_crash>
> <features>
> <acpi/>
> <apic/>
> <pae/>
> </features>
> <devices>
> <emulator>/usr/lib64/xen/bin/qemu-dm</emulator>
> <interface type='bridge'>
> <source bridge='xenbr0'/>
> <mac address='00:16:3e:0e:e8:b7'/>
> <script path='vif-bridge'/>
> </interface>
> <disk type='file' device='disk'>
> <driver name='file'/>
> <source file='/root/kernel.img'/>
> <target dev='hda'/>
> </disk>
> <input type='mouse' bus='ps2'/>
> <graphics type='vnc' port='-1' listen='0.0.0.0'/>
> <console tty='pty'/>
> </devices>
> </domain>
If we were to switch that domain to PV, the change would basically
to remove os/loader and devices/emulator, change os/type to be linux,
and then get kernel and initrd to point to the PV versions, right ?
No need to get rid of devices/emulator - that's valid for paravirt
guests too now - qemu-dm is used to provide the VNC / SDL framebuffer
and text console in paravirt guests too now. So merely remove loader
and the os/type to linux.
> + /*
> + * Originally XenD abused the 'kernel' parameter for the HVM
> + * firmware. New XenD allows HVM guests to boot from a kernel
> + * and if this is enabled, the HVM firmware must use the new
> + * 'loader' parameter
> + */
> + if (hasKernel) {
> + virBufferVSprintf(buf, "(loader '%s')", (const char *)
loader);
> } else {
> virBufferVSprintf(buf, "(kernel '%s')", (const char *)
loader);
> }
What happen if someone uses libvirt-0.4.1 with an old xend and an HVM
with kernel XML description is given ? I suppose (kernel) gets ignored
but it fails because the loader is not proper.
Yep, user error. If they try to use a kernel+initrd on an old XenD there's
nothing we can do to make it work. I don't want to do a Xen version check
in libvirt though, because this kernel+initrd stuff is something I backport
to the Xen currently in Fedora so any version check would be bogus.
Dan.
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