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RE: [Xen-devel] Question about evtchn_callback reentry

To: "Keir Fraser" <keir@xxxxxxxxxxxxx>
Subject: RE: [Xen-devel] Question about evtchn_callback reentry
From: "Xu, Anthony" <anthony.xu@xxxxxxxxx>
Date: Wed, 20 Dec 2006 18:08:02 +0800
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx, xen-ia64-devel <xen-ia64-devel@xxxxxxxxxxxxxxxxxxx>
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Thread-topic: [Xen-devel] Question about evtchn_callback reentry
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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