Re: booting from HVM (?pv?)

[George Dunlap <george.dunlap@eu.citrix.com>]

On 06/25/2013 11:47 AM, AL13N wrote:
>> On Mon, Jun 24, 2013 at 9:21 PM, AL13N <alien@rmail.be> wrote:
>>> Hi,
>>>
>>> I'm the Mageia XEN packager and during QA, we stumbled into a problem.
>>>
>>> in fact, we wanted to test Mageia 3 installation on a HVM.
>>>
>>> so, we had a sparse image and a iso file:
>>>
>>> [ 'file:/opt/testhvm.img,sda,w', 'file:/opt/mageialive.iso,hdb:cdrom,r'
>>> ]
>>>
>>> the live booted, and was able to install to disk, but it never seemed to
>>> boot
>>> after the install... (for some reason)
>>>
>>> in the end, this "worked" when we changed to:
>>>
>>> [ 'file:/opt/testhvm.img,xvda,w', 'file:/opt/testhvm.img,sda,w' ]
>>>
>>> apparently 'xvda' to get grub to boot the kernel; and 'sda' so that it
>>> could
>>> start...
>>
>> My HVM Linux config files have 'hda' instead of 'sda' -- can you try
>> that instead?
>>
>> Normally what happens is that qemu begins by exposing the hda device
>> to the guest, to boot via grub; but when the Xen PV drivers in the
>> Linux kernel come up, they write to a magic port which causes the
>> physical hda device to disappear.  I *think* then that the Xen PV
>> drivers actually take over that major/minor, so that further reads and
>> writes to the hda go through the PV protocol instead.
>>
>> All of this might get mixed up if you're using sda instead.
>>
>>   -George
>>
>
>
> well, hda is what we tried first, but we couldn't see the disk from the
> live system with hda. only sda seemed to work for that...

When you say, "we couldn't see the disk from the live system", you're 
talking about booting from the live CD?

If post-install you try 'hda' and it boots (after changing the grub and 
/etc/fstab if necessary), then I would suspect that there's a problem 
with your live CD kernel.  Do you use a different kernel image, and/or 
are the modules for the Xen PV devices not included?

  -George