RE: [Xen-ia64-devel] [PATCH] emulate PAL_HALT_LIGHT on domU

["Tian, Kevin" <kevin.tian@xxxxxxxxx>]

>From: Atsushi SAKAI
>Sent: 2006年7月5日 11:47
>
>Hi, All
>
>This patch emulates Guest PAL_HALT_LIGHT on domU by using
>do_block and timer.
>It also adds the function of the timer event sending to domU at the vcpu
>woke up.
>
>Signed-off-by: Atsushi SAKAI <sakaia@xxxxxxxxxxxxxx>
>
>
>About the timer event sending to domU
>
>The function "xen_timer_interrupt" on ParaVM/IA64 only sends
>the timer signal to current vcpu.
>When the idle domain is running, no domUx receives timer signal.
>If some domain cannot receive the timer signal during 10 secs,
>a message "BUG: soft lockup detected appeared" comes from domUx.
>To avoid this, I add a timer check routine at the vcpu woke up.
>

Hi, Sakai,
        Good catch, but... why do you need to choose minimal value from 
(s - now) and (d - now)? Vcpu_get_next_time only serves for target vcpu 
dedicatedly, and thus you only need to set an expiration value matching 
what guest wants - (vITM - vITC). This is not like vcpu_set_next_time 
which manipulates real mITM and needs to ensure other soft timer 
working properly.

        BTW, there's no need for vcpu_set_next_timer in hlt_timer_fn, since 
timer dispatcher will update mITM at end of scan loop and target vcpu 
hasn't update a new vITM value yet at that point.

Thanks,
Kevin

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