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

[Juergen Gross <jgross@xxxxxxxx>]

On 12/11/15 12:32, Wei Liu wrote:
> On Thu, Nov 12, 2015 at 12:29:06PM +0100, Juergen Gross wrote:
>> 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.
>>
>>
> 
> I think we use pvgrub to denote the third case (according to our wiki).
> The second case is just ... upstream grub2 with pv capability ?

Urgs. Okay. Nevertheless: I've built it. :-)

> (So many grubs...)

I'm particularly happy you didn't come up with a variant I wasn't aware
of. :-)


Juergen


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