Re: [Xen-devel] [PATCH v4 1/9] libxc: reorganize domain builder guest memory allocator

[Juergen Gross <jgross@xxxxxxxx>]

On 12/11/15 12:20, Ian Campbell wrote:
> On Thu, 2015-11-12 at 11:14 +0000, Wei Liu wrote:
>> On Thu, Nov 05, 2015 at 03:36:27PM +0100, Juergen Gross wrote:
>>> Guest memory allocation in the domain builder of libxc is done via
>>> virtual addresses only. In order to be able to support preallocated
>>> areas not virtually mapped reorganize the memory allocator to keep
>>> track of allocated pages globally and in allocated segments.
>>>
>>> This requires an interface change of the allocate callback of the
>>> domain builder which currently is using the last mapped virtual
>>> address as a parameter. This is no problem as the only user of this
>>> callback is stubdom/grub/kexec.c using this virtual address to
>>> calculate the last used pfn.
>>>
>>> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
>>
>> One question: did you test building with pygrub after this change? I
>> think the code is correct but we'd better be sure it doesn't break
>> pygrub.
> 
> Did you mean pvgrub? (with a Vee)
> 
> pygrub (with a Why) runs way before the libxc domain builder gets in on the
> act, doesn't it.

Yep.

To be clear: we have:

- pygrub: running on dom0, mounts the root disk and analyzes the grub
  configuration found, selects kernel and initrd and loads those via
  libxl.

- pvgrub: based on grub2, is started via libxl as paravirtualized kernel
  in the new domain. pvgrub is reading the grub configuration and starts
  the appropriate kernel via it's own mechanisms (patches for support of
  huge domains are sent, no comments up to now).

- stubdom based grub: subject to the patch we are discussing here. It is
  being built in my environment, but not tested up to now.


Juergen


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