Re: [Xen-devel] Guidance for PVHv2 usage?

[PGNet Dev <pgnet.dev@xxxxxxxxx>]

On 5/29/17 10:03 AM, Roger Pau Monné wrote:
>> IIUC, Xen 4.9 + kernel-default > v4.11 should now fully support PVHv2?
> 
> For DomUs yes, for Dom0 not yet.

thx

> Forget about this document, I should have removed it as part of the
> PVHv1 code removal. In any case, those where PVHv1 internal details,
> that are to no use to the end user.

noted

>> Is that the case already?  Or is there a transition state in effect, where 
>> both are available?
> 
> Almost, Xen is still currently transitioning from PVHv1 to PVHv2.
> PVHv1 is not available anymore, and PVHv2 is still experimental (and
> not finished in the Dom0 case).

Aha.  The still-experimental state wasn't immediately clear from the Phoronix 
article's "... Lands ..." title.

>>      GRUB_CMDLINE_XEN="dom0=hvm dom0_mem=4G,max:4G dom0_max_vcpus=4 ..."
>>                        ^^^^^^^^
> 
> I guess this is in the Dom0 grub config file?

Yes / Sry, should've been clearer on that.

> In any case, please
> hold off before trying Dom0, it's still not in a working state.

Does "hold off" -- in this fuzzy interim -- simply mean -- do NOT specify any 
dom0=XXX?  Or to specify dom0=pvh, or somesuch?

>> and in Guest.cfg
>>
>>      builder = 'linux'
>>      kernel = '/usr/lib/grub2/x86_64-xen/grub.xen'
>>      xen_platform_pci = 1
>>      device_model_version = 'qemu-xen'
>>      ...
> 
> I'm not really sure what this guest is, PV I assume?

Heh.  Well, that's a good question.

It WAS hvm, and now it's TRYING to be PVHv2.  It's booted atm as SOMETHING ... 
I suppose it's 'still' PVH.

That^ config IS what I *used* to use for PVH on Opensuse ...

> builder = 'linux' is not a valid option [0].

It is -- or at least, WAS -- for Opensuse's Xen:

   https://lists.opensuse.org/opensuse-virtual/2016-01/msg00004.html

Also referenced here:

   https://patchwork.kernel.org/patch/9368403/


I've been running only HVM guests for awhile, so I am NOT certain that hasn't 
changed ...

In any case, the Guest *IS* launching with builder=linux, with no complaint at 
the moment.

Unclear, then, what that means if it is, in fact, NOT a valid option.

> Also grub.xen (which I imagine is pvgrub)

It's from grub2

 rpm -q --whatprovides /usr/lib/grub2/x86_64-xen/grub.xen
  grub2-x86_64-xen-2.02-3.3.x86_64

which I thought makes it pvgrub2?  Not that it matters since, apparently

> is not going to work for PVHv2,


> you will have to
> direct boot into the kernel you wish to use. For example a suitable
> config file for PVHv2 would be:
> 
> builder='hvm'
> device_model_version='none'
> 
> kernel='/path/to/kernel'
> ramdisk='/path/to/initrd'


so, just to be clear, for PVHv2, we'll use =HVM, not PVH (=generic), builder? 
Even given that PVHv1 is not available anymore, and it _sounds_ like PVHv2 will 
"replace" PVH?

> Note that this is a temporary interface, this is subject to change.

sure.  hence, 'testing' ...

> Since the interface is not yet finished, no, there are no current docs
> available, sorry.

Thanks.

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