RE: [Xen-devel] Question about evtchn_callback reentry

["Xu, Anthony" <anthony.xu@xxxxxxxxx>]

Keir Fraser write on 2006年12月20日 16:31:
> On 20/12/06 3:03 am, "Xu, Anthony" <anthony.xu@xxxxxxxxx> wrote:
> 
> How did you implement nesting avoidance? It'll be a bit subtle to get
> right. 

I added another global_event_mask in share page.

1. before injecting to event_callback_handler, set global_event_mask to 1 to 
   disable event inject..
2. after event_callback_handler is executed, it will return to ia64_leave_kernel
    assembly code in dom0, in this assembly code, it sets global_event_mask to 0
    to enable event inject.

There is no other code operating the global_event_mask.
Global_event_mask is initiated to 0(unmask).

Only global_event_mask is 0 and vcpu->vcpu_info->evtchn_upcall_mask is 0,
Can XEN injects to event_callback_handler of dom0.

--Anthony





> 
>  -- Keir

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