Re: [PATCH 1/4][Xen-devel] X86 microcode: cancel redundant input parameter of microcode functions

Christoph Egger
2009-01-22T11:07:49Z

On Thursday 22 January 2009 11:54:15 Liu, Jinsong wrote:
> Christoph Egger wrote:
> > On Thursday 22 January 2009 04:08:21 Liu, Jinsong wrote:
> >> X86 microcode: cancel redundant input parameter of microcode
> >> functions
> >>
> >> Cancel redundant input parameter ''uci'', since it
can get from
> >> another input parameter ''cpu'' as index.
> >>
> >> Signed-off-by: Liu, Jinsong <jinsong.liu@intel.com>
> >
> > I added the parameter ''uci'' to reduce dependency on
a global variable.
> > That improves reentrancy and cache locality.
> >
> > If you want to go a step forward rather back, then remove the
''cpu''
> > parameter instead.
> >
> > Christoph
>
> I think the input parameter ''cpu'' is better than
''uci'' since ''cpu'' is much
> clear to developer with explicit meaning, so between the 2 redundant
> parameters ''uci'' and ''cpu'', we should
remove ''uci'', just like what native
> linux microcode functions do.

What linux does, doesn''t matter here. Dom0 just has to make the
hypercall.
This is nothing linux specific.

> As for cache locality, it''s not important for microcode functions
since
> it''s not in key path, seldom be called.

Right, but better reentrancy is always good.

> BTW, we''d better keep consistent
> with native linux code for the sake of futher porting and upgrade, you
> know, the latest linux kernel (2.6.28) still has some issues for microcode
> ...

You should have hear yourself.

Someone else can say:

BTW, we''d better keep consistent
with native Solaris code for the sake of further porting and upgrade. It
doesn''t suffer on the Linux issues.

And another guy can say:

BTW, we''d better keep consistent with native BSD code for the sake
of further porting and upgrade.


You see what I mean?


Christoph


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