RE: [Xen-ia64-devel][PATCH] Enable SMP on VTI domain.

["Xu, Anthony" <anthony.xu@xxxxxxxxx>]

>From: Isaku Yamahata [mailto:yamahata@xxxxxxxxxxxxx]
>Sent: 2006?6?1? 12:45
>> >I just took a quick look at your patch though.
>> >There is no protection to IPI.
>> >Is it O.K? Does the use of IPI cause race?
>> >
>> Do you mean below code?
>> #ifdef XEN
>>      spin_lock(&call_lock);
>> #else
>
>I meant local_irq_save(), local_irq_restore(). masking ipi.
>
I'm not sure.
But I don't think it is needed, otherwise how a LP sends IPI to itself.
>
>> Or you mean the protection of global purge.
>> When a vcpu get IPI to purge TLB,
>> What it does is to invalid the TLB entry in VHPT,
>> but not remove the TLB entry.
>> There is no race condition.
>
>Is there any gurantee that the vcpu which recives IPI isn't touching VHPT?

The vcpu which receives IPI can touch VHPT in the same time.
Because purge operation only sets the TLB entry invalid, like entry->ti=1.
That has the same philosophy with Tristan's direct purge


>
>--
>yamahata

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