Re: [Xen-users] pvgrub2(-like?) booting methods for PVHv2 guests

[Hans van Kranenburg <hans@xxxxxxxxxxx>]

On 01/25/2018 03:31 PM, Juergen Gross wrote:
> On 25/01/18 15:12, Hans van Kranenburg wrote:
>> On 01/25/2018 02:46 PM, Hans van Kranenburg wrote:
>>> On 25/01/2018 13:29, Juergen Gross wrote:
>>>> On 25/01/18 13:19, Andy Smith wrote:
>>>>> Hi Hans,
>>>>>
>>>>> On Thu, Jan 25, 2018 at 12:39:56PM +0100, Hans van Kranenburg wrote:
>>>>>> And now I get console output and things happen. Only it can't find the 
>>>>>> disk.
>>>>>
>>>>> I was trying similar thing (4.10 and PVH) and also ended up with a
>>>>> guest with no block devices. I reported this on grub-devel:
>>>>>
>>>>>     <http://lists.gnu.org/archive/html/grub-devel/2018-01/msg00018.html>
>>>>>
>>>>> as I was thinking this was not a Xen problem since same thing boots
>>>>> okay outside grub with direct kernel boot.
>>>>>
>>>>> Juergen did reply and said I needed this kernel patch in the guest:
>>>>>
>>>>>     <https://lists.xen.org/archives/html/xen-devel/2017-11/msg01681.html>
>>>>>
>>>>> But I think you have this don't you?
>>>
>>> Yes, see my earlier mail with all the steps that I did, step 6.
>>>
>>>> As the ACPI tables are found, I'd say yes. :-)
>>>
>>> dmesg output is pretty different when I boot directly with the kernel
>>> and initrd copied on the dom0.
>>>
>>> Remember, it's the same kernel/initrd, and without grub in between it
>>> boots with all vcpus network and disk.
>>>
>>> With grub in between, this at least does look suspicious:
>>>
>>> [    0.032110] PCI: System does not support PCI
>>
>> Eh, that's in both, stay awake Hans.
>>
>>> And yes, there are also no successful netfront lines.
>>>
>>> Without grub: http://paste.debian.net/plainh/7120cef2
>>> With grub: http://paste.debian.net/plainh/426bed60
>>
>> Or the diff between them, which shows what changes when inserting grub
>> in between:
>>
>> http://paste.debian.net/plainh/52b2d618
>>
>> I must admit I don't know too much (yet) about all those changed lines,
>> but this next is also a very interesting change?...
>>
>> -Booting paravirtualized kernel on Xen PVH
>> +Booting paravirtualized kernel on Xen HVM
> 
> Aah, yes, this should be the reason for the problems.
> 
> I addressed the ACPI problem first. What is missing now is to set PVH
> mode when booting via grub.
> 
> So please stay tuned...

For my info... Is this something like flipping a bit somewhere, or will
it involve a whole lot more complicated wizardry?

Real question is of course if there's a PoC solution to apply that I can
use now? ;-] I'm throwing custom build kernels at my test environment,
and if I could save the time (and mistakes) of manually editing the
guest files and instead hit the pvgrub2+PVHv2 path many times to test...

Hans

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