Re: [Xen-devel] [PATCH v2 2/5] vm_event: Implement ARM SMC events

[Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>]

On 05/04/2016 04:26 PM, Julien Grall wrote:
> I may misunderstand some parts of the vm event subsystem. To get/set the
> full set of registers, the user will have to use the
> DOMCTL_{set,get}vcpucontext, correct? So why does Xen expose a part of
> the vCPU context through the vm_event?

Because DOMCTL_{set,get}vcpucontext is expensive, and a serious
introspection application will receive hundreds or thousands of events
per second.

Having what's most commonly needed being sent with the vm_event
eliminates the need for extra hypercalls and can make the difference
between a responsive and an unusable userspace introspection application.


Thanks,
Razvan

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