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

[Hans van Kranenburg <hans@xxxxxxxxxxx>]

On 02/06/2018 06:02 PM, Juergen Gross wrote:
> On 06/02/18 17:53, Hans van Kranenburg wrote:
>> 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
> 
> You didn't add the RSDP detection patch, right? In the log I see:
> 
> ACPI BIOS Error (bug): A valid RSDP was not found (20170831/tbxfroot-244)

Yes, I didn't have those. Argh...

However, after putting the 'xen: re-enable booting as Xen PVH guest' v2
patches on top, same happens.

ACPI BIOS Error (bug): A valid RSDP was not found ...

When taking pvgrub2 out and directly booting a copy of the
kernel/initrd, it does actually boot:

http://paste.debian.net/plainh/896936d4

So, the pvgrub2 path is now borken again?

My pvgrub2 binary is still the same one as before.

Hans

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