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

["Jan Beulich" <JBeulich@xxxxxxxxxx>]

>>> 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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