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Re: [Xen-devel] [PATCH] tools/libxl: make default of max event channels dependant on vcpus

On 26.03.20 13:36, Andrew Cooper wrote:
On 26/03/2020 09:45, Juergen Gross wrote:
Today the maximum number of event channels for a guest is defaulting
to 1023. For large guests with lots of vcpus this is not enough, as
e.g. the Linux kernel uses 7 event channels per vcpu, limiting the
guest to about 140 vcpus.

Instead of requiring to specify the allowed number of event channels
via the "event_channels" domain config option, make the default
depend on the maximum number of vcpus of the guest.

In order not to regress current configs use 1023 as the minimum
default setting.

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>


I suspect I regressed this by making it not actually dead code.

1023 is the 32bit EVT 2L ABI limit, but until I moved max_evtchn into
the createdomain hypercall, I'm pretty sure a limit never used to get set.

In 4.11 I'm seeing it being set via xc_domain_set_max_evtchn().




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