RE: [Xen-ia64-devel] [PATCH] unify vtlb and vhpt

[Kouya Shimura <kouya@xxxxxxxxxxxxxx>]

Dong, Eddie writes:
>  TLB. The issue in today's Xen/IA64 is
> that so called vTLB is not equal to real guest TLB. (guest TLB
> = vTR + vTLB + something in VHPT + something in machine TLB)
> 
> If you want to rename vTLB to something else, I will vote for Yes.

Yea, vTLB should be renamed vTC.

> Sharing memory makes concept clear for me. I.e. VHPT is VHPT,
> while vTLB is those entries can't be put into VHPT.
> 
> With this patch, if a VTLB entry in collision chain has to become
> head of VHPT table, it is really dilemma to put this to head or not.
> GP fault for reserved bit could be used here with performance 
> penalty but it is really not good and it could happen again as if the
>  VHPT entry head keeps for vTLB (TC could go away soon).

??? a vTLB entry never be inserted to head.
Xen has a responsibility for it. 
The reserved bit fault is a just insurance.

> Limiting the entry to be not moved to VHPT head could solve this
> issue but again the code will be complicated.
> 
> Sharing VTLB/VHPT memory could be simply used here, and the patch
> will be more smaller and simple IMO.

My concept is just sharing vTLB/VHPT memory. 
As long as sharing the pool of collision chain,
distinction of vTLB/VHPT can't be avoided

Thanks,
Kouya

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