RE: [Xen-ia64-devel][Patch]Add two PAL calls which fixSMPwindowsinstallation crashing bug

["Zhang, Xing Z" <xing.z.zhang@xxxxxxxxx>]

Hi Kouya and Tristan:
        I still have a question. After "11.XEN stops the vcpu", APs wait in 
Xen, how does BSP wake up them again? I don't think BSP will send an IPI to 
them again.
In windows, seems BSP will wait a very short time for AP waking up. Whiles APs 
waked up, they will fall into a loop to wait another times waking up by BSP.
But this time, BSP use memory semaphore to do that but not an IPI. 
En, maybe something I lost, hope your comments.

Good good study,day day up ! ^_^
-Wing(zhang xin)
 
OTC,Intel Corporation

>-----Original Message-----
>From: xen-ia64-devel-bounces@xxxxxxxxxxxxxxxxxxx
>[mailto:xen-ia64-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Kouya
>SHIMURA
>Sent: 2007年4月5日 13:52
>To: Tristan Gingold
>Cc: xen-ia64-devel
>Subject: Re: [Xen-ia64-devel][Patch]Add two PAL calls which
>fixSMPwindowsinstallation crashing bug
>
>Tristan Gingold writes:
> > > In 10, I don't understand why the special SAL_XEN_SAL_RETURN is
> > > necessary instead of PAL_HALT. The difference is test_and_set_bit() or
> > > set_bit(). I think a vcpu with VCPU_down state never be at this point.
> > > Besides calling vcpu_sleep_no_sync() with VCPU_down state seems to be
> > > harmless.
> > Humm, to be discussed:
> > Although the implementation may be almost the same, I think the semantic is
> > not.
> > After SAL_XEN_SAL_RETURN, the processor can be awaken only by a rendez-vous.
> > Its state is reset.
> >
> > After PAL_HALT, the processor can be awaken by an IPI. Its state is 
> > preserved.
> >
> > Tristan.
>
>I see. For example, preserving a vcpu context is unnecessary after
>SAL_XEN_SAL_RETURN for save/restore of a domain.
>
>Thanks,
>Kouya
>
>
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