[Xen-devel] Question about event channels and masking event channels

[Rick <judicator3@xxxxxxxxx>]

Hello,

There is something I do not undestand about the event handling
mechanism in xenolinux.
XenoLinux can listen for 1024 events (0 to 1023). The shared_info_t
structure records the pending and the masking of events using the
following bit vectors:
=================================================
u32 evtchn_pending[32]; 
u32 evtchn_pending_sel; 
u32 evtchn_mask[32]; 
=================================================

Next, I am looking at the function mask_evtchn() in the file evtchn.h
=================================================
static inline void mask_evtchn(int port)
{
    shared_info_t *s = HYPERVISOR_shared_info;
    synch_set_bit(port, &s->evtchn_mask[0]);
}
=================================================

Why do we only focus on evtchn_mask[0] ?
I thought that Port would be a number between 0 to 1023 and masking
the correct bit would be done with something like that:
synch_set_bit(port%32, &s->evtchn_mask[port/32]);

Is it the case that one can only mask out the first 8 bits in evtchn_mask[0] ?

Thanks
Rick


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