Re: [Xen-devel] booting from HVM (?pv?)

["AL13N" <alien@xxxxxxxx>]

> On 06/25/2013 11:47 AM, AL13N wrote:
>>> On Mon, Jun 24, 2013 at 9:21 PM, AL13N <alien@xxxxxxxx> 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?

what i mean is:

1st try was using hda en hdb:cdrom with an iso and boot=dc

this booted from the livecd, but the disk was not visible, even though
xenblk_front was loaded (does hvm use a different module for emulation?
there were some ide modules loaded as well).

this is one thing we wanted to get right when having Mageia to be
xen-ready (ie: installable on HVM from iso)

We'll try using hda postinstall...


PS: one weird thing that i saw in the log files, was a message about
stripping tap from device, which was odd, since file:/... was specified
and not tap:aio:... (and Mageia 3 doesn't have a specific -xen kernel, nor
a blktap-dkms...)


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