Re: [Xen-devel] [PROPOSAL] Event channel for SMP-VMs: per-vCPU or per-OS?

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 29.10.13 at 03:56, Luwei Cheng <chengluwei@xxxxxxxxx> wrote:
> Hmm.. though all vCPUs can serve the events, the hypervisor delivers the
> event to only "one" vCPU at at time, so only that vCPU can see this event.
> Analytically no race condition will be introduced.

No - an event is globally pending (at least in the old model, the
situation is better with the new FIFO model), i.e. if more than
one of the guest's vCPU-s allowed to service it would be looking
at it simultaneously, they'd still need to arbitrate which one
ought to handle it.

So your proposed extension might need to be limited to the
FIFO model.

Jan


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