RE: [Xen-devel] pre-reservation of memory for domain creation

["Xu, Dongxiao" <dongxiao.xu@xxxxxxxxx>]

Keir, I will work on that.

Thanks!
Dongxiao

Keir Fraser wrote:
> It's either that or stub out the feature (return to previos #VCPUs
> limit) I think.
> 
>  -- Keir
> 
> On 13/01/2010 02:34, "Xu, Dongxiao" <dongxiao.xu@xxxxxxxxx> wrote:
> 
>> If we didn't add this change, as Keir said, Xen will crash during
>> destruction of partially-created domain. However I didn't noticed
>> the toolstack and shadow_min_acceptable_pages() side at that time...
>> For now, should we adjust the shadow pre-alloc size to match
>> shadow_min_acceptable_pages() and modify toolstack accordingly? 
>> 
>> Thanks!
>> Dongxiao
>> 
>> Jan Beulich wrote:
>>>>>> Keir Fraser <keir.fraser@xxxxxxxxxxxxx> 12.01.10 16:53 >>>
>>>> On 12/01/2010 15:32, "Jan Beulich" <JBeulich@xxxxxxxxxx> wrote:
>>>> 
>>>>> Also - how did that fixed amount get determined?
>>>>> shadow_min_acceptable_pages() says 128 pages per vCPU, but 4Mb
>>>>> (1024 pages) is not matching this (given that it ought to be fine
>>>>> for 128 vCPU-s), just as the old value of 1Mb wasn't matching the
>>>>> supposed need of 32 vCPU-s.
>>>> 
>>>> I'm not sure I really believe the toolstack comment. As you say, it
>>>> wasn't correct before or after the patch we're talking about.
>>> 
>>> The tool stack comment was correct before that patch; it isn't now.
>>> The size in shadow_enable() doesn't match
>>> shadow_min_acceptable_pages(), but that's all hypervisor code.
>>> 
>>> And that's also no answer to the question on where the particular
>>> value came from (and namely why it being much smaller than what
>>> shadow_min_acceptable_pages() would determine still isn't going
>>> to be a problem).
>>> 
>>>>> And btw., I think that papering over a Xen crash during
>>>>> destruction of partially-created domain is rather bad a thing to
>>>>> do. 
>>>> 
>>>> Depends on whether domain-creation failure at the point it failed
>>>> -- and due to inadequate pre-reservation -- is expected and
>>>> allowed for by the HVM paging logic.
>>> 
>>> So you say it's acceptable for a flaw in the tools (exposed during
>>> guest creation) to bring down the whole machine?
>>> 
>>> Jan
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