Re: [Xen-devel] One question about the hypercall to translate gfn to mfn.

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 15.12.14 at 16:22, <stefano.stabellini@xxxxxxxxxxxxx> wrote:
> On Mon, 15 Dec 2014, Jan Beulich wrote:
>> >>> On 15.12.14 at 10:05, <kevin.tian@xxxxxxxxx> wrote:
>> > yes, definitely host RAM is the upper limit, and what I'm concerning here
>> > is how to reserve (at boot time) or allocate (on-demand) such large PFN
>> > resource, w/o collision with other PFN reservation usage (ballooning
>> > should be fine since it's operating existing RAM ranges in dom0 e820
>> > table).
>> 
>> I don't think ballooning is restricted to the regions named RAM in
>> Dom0's E820 table (at least it shouldn't be, and wasn't in the
>> classic Xen kernels).
> 
> Could you please elaborate more on this? It seems counter-intuitive at best.

I don't see what's counter-intuitive here. How can the hypervisor
(Dom0) or tool stack (DomU) know what ballooning intentions a
guest kernel may have? It's solely the guest kernel's responsibility
to make sure its ballooning activities don't collide with anything
else address-wise.

Jan


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