Re: [Xen-devel] [PATCH v3 1/3] libxl: xl mem-max et consortes must update static-max in xenstore too [and 1 more messages]

[George Dunlap <dunlapg@xxxxxxxxx>]

On Wed, Apr 10, 2013 at 4:56 PM, Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx> wrote:
> Daniel Kiper writes ("Re: [Xen-devel] [PATCH v3 3/3] xl: Improve xl 
> documentation in regards to guest memory management"):
>> No, memory hotplug should not change "static maximum" in any case.
>
> Why shouldn't it ?

FWIW, at least XenServer uses "static max" to mean "cannot be changed
except by rebooting".  It *also* uses *that* for HVM guests to say
"how much memory to advertize to the guest".  That is, if you boot a
VM with memory = X and static_max = Y, then it will put Y amount of
memory in the virtual e820 map, allocate X memory for the PoD, and
then rely on the balloon driver to balloon from Y down to X during
boot.

This is two slightly different meanings -- "how much to put in the
guest e820" and "how much maximum a guest is ever allowed to have".
The plain meaning of "static max" should be the second (i.e., can't be
changed dynamically at run time).  If we want a "max in the e820 at
build time" we should probably come up with a new term; and if "how
much the guest is ever allowed to have without rebooting" is not a
useful concept, we should probably just discard it.

 -George

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