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

[Hans van Kranenburg <hans@xxxxxxxxxxx>]

On 02/06/2018 09:35 AM, Juergen Gross wrote:
> On 05/02/18 20:49, Hans van Kranenburg wrote:
>> 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...
> 
> So I looked into this briefly and discovered that my memory really needs
> the backup I have on my hard disk: you want commit
> 418492ba40b2c2bbdaf1a169aac5b1673bde8189 which was for 4.15.

Aha. Well, I can as well better jump to 4.15 now, since picking that
patch on 4.14.17 shows I need more other patches it depends on, related
to struct x86_legacy_features and x86_hyper_init reorganization.

So, I just built a 4.15.1 kernel (using gcc 7.2.0), which definitely has
this one in it:
  418492ba40b2 x86/virt/xen: Use guest_late_init to detect Xen PVH guest

I can boot via pvgrub2 (the Xen that's running now is current
stable-4.10 plus the RSDP for PVH guest near 4GB patch).

But, it still tells me...
  Booting paravirtualized kernel on Xen HVM

...and then hangs somewhere halfway.

Full boot log here: http://paste.debian.net/plainh/ae3ea14b

Hans

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