Re: [Xen-ia64-devel] [PATCH][RFC][TAKE4] the P2M/VP patches

[Isaku Yamahata <yamahata@xxxxxxxxxxxxx>]

On Fri, Apr 07, 2006 at 03:57:30PM +0800, Tian, Kevin wrote:
> >> Does this patch only save one hypercall overhead? We can always
> >> tell guest the auto_translated bit is true when guest hypercalls to
> >> query feature bits into xen_feature array.
> >
> >No.
> >I agree that we can go without this patch by telling the bit always 1.
> >The reasons why I wrote this patch are as follows
> >
> >- It is more explicit than telling auto_translated bit always 1.
> >  Perhaps code readers expect that the auto_translated feature
> >  can be determined at run-time even for xen/ia64, not requirement.
> >  This is only a readability issue.
> >  Telling auto_translated bit 1 makes code harder-to-read a bit.
> >
> >- Compiler can optimize better.
> 
> Maybe I'm not clear here. You can see from setup_xen_features 
> where a hypercall is issued to query what on earth this domain is 
> configured with. That feature info can be passed in from config file. 
> So I think even xen/ia64 wants to hardcode auto_translated bit as 1, 
> it's better to do within xen with xenlinux inferface unchanged to query. 
> Anyway, we don't want to eliminate future possibility that dom0 may 
> also see physmap directly for performance. :-) But yes, seems this 
> feature need to be queried earlier which seems difficult for current 
> xen/ia64 model. So it may be better to hardcode xen_features array 
> for now.
> 
> How do you think?

In fact I wondered that this patch was acceptable.
I guess that xen/x86 people will be against this patch saying similar
things.
This patch is not important, just for my preference.
I drop this patch.

-- 
yamahata

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