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

[Christoph Egger <Christoph.Egger@xxxxxxx>]

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@xxxxxxxxx>
> >
> > 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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