Re: [Xen-devel] [PATCH 0/5] xen: better grant v2 support

[Juergen Gross <jgross@xxxxxxxx>]

On 23/08/17 11:41, Jan Beulich wrote:
>>>> On 23.08.17 at 11:19, <jgross@xxxxxxxx> wrote:
>> Just some thoughts on that topic from my side:
>>
>> This approach should be fine IMO for memory allocated while creating a
>> domain. This is basically the same as a bare metal system where the BIOS
>> needs some memory.
>>
>> Memory allocated during the lifetime of a domain is a different problem:
>> either you allow the domain to claim more memory as configured, or you
>> have to reserve a more or less arbitrary amount of memory to be
>> allocated later and eventually fail such allocations. I don't think this
>> approach is acceptable.
> 
> Or an interrupt gets sent to the guest telling it that it should
> nominate (balloon out or something similar) a page in order for
> another of its operations to succeed. Of course that would be
> limited to paravirtual operations (i.e. mostly hypercalls);
> allocations done while emulating something could not be
> handled this way.

As this would probably break existing pv guests I don't think this
is an option we should consider.


Juergen

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