Re: [PATCH 0/5] libxc: support building large pv-domains

[Juergen Gross <jgross@suse.com>]

On 09/11/2015 03:53 PM, Ian Campbell wrote:
> On Fri, 2015-09-11 at 15:42 +0200, Juergen Gross wrote:
>> On 09/11/2015 03:28 PM, Ian Campbell wrote:
>>> On Fri, 2015-09-11 at 14:32 +0200, Juergen Gross wrote:
>>>> The Xen hypervisor supports starting a dom0 with large memory (up to
>>>> the TB range) by not including the initrd and p2m list in the initial
>>>> kernel mapping. Especially the p2m list can grow larger than the
>>>> available virtual space in the initial mapping.
>>>>
>>>> The started kernel is indicating the support of each feature via
>>>> elf notes.
>>>>
>>>> This series enables the domain builder in libxc to do the same as the
>>>> hypervisor. This enables starting of huge pv-domUs via xl.
>>>>
>>>> Unmapped initrd is supported for 64 and 32 bit domains, omitting the
>>>> p2m from initial kernel mapping is possible for 64 bit domains only.
>>>>
>>>> Tested with:
>>>> - 32 bit domU (kernel not supporting unmapped initrd)
>>>> - 32 bit domU (kernel supporting unmapped initrd)
>>>> - 1 GB 64 bit domU (kernel supporting unmapped initrd, not p2m)
>>>> - 1 GB 64 bit domU (kernel supporting unmapped initrd and p2m)
>>>> - 900GB 64 bit domU (kernel supporting unmapped initrd and p2m)
>>>>
>>>> Juergen Gross (5):
>>>>     libxc: remove allocate member from struct xc_dom_image
>>>>     libxc: do initrd processing of domain builder in own function
>>>>     libxc: create unmapped initrd in domain builder if supported
>>>>     libxc: split p2m allocation in domain builder from other magic
>>>> pages
>>>>     libxc: create p2m list outside of kernel mapping if supported
>>>>
>>>>    tools/libxc/include/xc_dom.h |   4 +-
>>>>    tools/libxc/xc_dom_core.c    | 123 +++++++++++++++++++++++++++++---
>>>> -----------
>>>>    tools/libxc/xc_dom_x86.c     | 120
>>>> ++++++++++++++++++++++++++++++++++++++++-
>>>
>>> How much is this going to conflict with Roger's "Introduce HVM without
>>> dm
>>> and new boot ABI" changes to HVM building?
>>
>> As it is touching the pv domain builder only, I don't think there will
>> be a conflict.
>
> The reason I asked is that the first thing Roger's series does is cause HVM
> domains to be built using the PV domain builder...

Aah, okay.

OTOH I'm doing nothing different than the hypervisor when loading dom0.
As long as the ELFNOTEs in question (or the corresponding elements in
dom->parms) are not set, the resulting domain image should be the same
as today.

>>   All rights of being wrong reserved. :-)
>
> Warranty void to the limit of your statutory rights ;-)

Ha, good intuition! The disclaimer wasn't a bad idea at the end. ;-)


Juergen