RE: [Xen-ia64-devel] Some things to be considered for ptc.ga emulation

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

>From: Tristan Gingold [mailto:Tristan.Gingold@xxxxxxxx]
>Sent: 2006年4月5日 17:28
>> the lock
>>                      * Only vcpu_translate stamps tlb_inuse count
>> now.
>> However all places with access needs same lock sense like tlb
>insertion
>> emulation.
>I am not sure about that.
>If both are writing, we can have incomplete insertion (eg: only dtlb but no
>vhpt nor itc), but it shouldn't matter.

As we talked previously, the effect of purge may be override by another 
write if both writing without lock protection.

>>                      * Lack of region id information. For a hash
>> version tlb, need
>> region id to calculate hash value of target entry. Since in different
>> context, region id switch is still required.
>Unless this is done in the context of the cpu doing ptc.ga.

Yes, that's the case for direct purge.

>
>>      Suggestion: it's natural/efficient to issue IPI to flush VHPT
>> table of
>> other LPs. If that's the case, why not integrate vcpu purge together
>> with IPI?
>Natural yes, efficient not sure.

Ah, efficient here doesn't mean efficiency right for purge emulation, which 
better means no influence to normal vhpt access on the right LP. For 
direct purge, you need to add lock at all places with access to VHPT 
table. :-)

>I think this describes correctly the IPI way.

Yes.

>
>BTW, I am still working on direct purge.
>

Sure. You can post again once ready and people can see whether it 
addresses concerns.

Thanks,
Kevin

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