RE: [Xen-devel] [PATCH] Pin vcpu for VMX domain

["Jiang, Yunhong" <yunhong.jiang@xxxxxxxxx>]

>Rather than calling vmx_remove_timers() from your SMP call function, 
>can you not just call it from vmx_reinstall_timers()? 

I'm not sure if it will has some corner case, and hope your
clarification for it.
considering following situation, assume the VMX switch from cpu 0->cpu1
1) on cpu0, the timer interrupt happened, so timer_softirq_action is
called, the pit_timer_fn is called, and in pit_timer_fn, it will try to
set the  pit timer again.
2) before pit_timer_fn set the pit timer on cpu0, the stop_timer is
called on cpu1 on vmx_reinstall_timers. 
3) after stop_timer finished, the pit_timer_fn on cpu0 set the ac_timer
on cpu0.

on this situation, the stop_timer on cpu1 will has no effect. And then
the init_timer may cause error situation.

In fact, I think the old patch itself is not safe on this situation,
since the stop_timer is called on IPI interrupt , which may run when the
pit_timer_fn is running.



>You explain why 
>the pit and hlt timers do not need to be re-activated in 
>vmx_reinstall_timer() -- what about the APIC timer?
>

The APIC timer should be same to PIT timer in future and a patch is
needed for this, I had a comments for it and deleted when clean coding
style.

Thanks
Yunhong Jiang

>There's no need to check active_timer() before calling stop_timer() -- 
>stop_timer does the check for you.
>
>  -- Keir
>

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