Re: [Xen-devel] [PATCH v1] libxl: remove limit for default number of event channels

[Jan Beulich <jbeulich@xxxxxxxx>]

On 27.03.2020 15:37, Olaf Hering wrote:
> On Fri, Mar 27, Ian Jackson wrote:
> 
>> This seems likely to be right, but: what is the default in Xen ?  Is
>> it sufficiently tight to stop a guest using too many resources ?
> 
> The value of d->max_evtchns will be either 4k or 128k.
> AFAICS no extra resources are allocated with the changed value.

Of course there are, as soon as the guest uses the event channels.
Did you see Jürgen's patch sent earlier this week, aiming to
address the same issue of larger vCPU counts being a problem
("tools/libxl: make default of max event channels dependant on
vcpus")? See the discussion there.

Jan