[Xen-devel] Re: [PATCH] CPUID level 0x00000007:0 (ebx) is word 9

To:	Jan Beulich <JBeulich@xxxxxxxxxx>, Xin Li <xin.li@xxxxxxxxx>
Subject:	[Xen-devel] Re: [PATCH] CPUID level 0x00000007:0 (ebx) is word 9, instead of word 7
From:	Keir Fraser <keir.xen@xxxxxxxxx>
Date:	Wed, 01 Jun 2011 07:47:24 +0100
Cc:	xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>
Delivery-date:	Tue, 31 May 2011 23:48:51 -0700
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On 01/06/2011 07:35, "Jan Beulich" <JBeulich@xxxxxxxxxx> wrote:

>>>> On 31.05.11 at 16:59, "Li, Xin" <xin.li@xxxxxxxxx> wrote:
>>> can't see why we would need to stay in sync with Linux's capability
>>> array indices.
>> 
>> why?  Typically we reuse Linux code unless Xen has its special logic.
> 
> So you would suggest leaving indices 7 and 8 unused instead?
> Looking at current Linux, we certainly could convert Xen to use
> index 8 for virtualization features, but since these are being
> tracked differently already anyway I don't see a value in this.
> 
> As to index 7, just look at ARAT - we're already diverging from
> Linux here (having it allocated in index 3).
> 
> Bottom line is that I think keeping the names (and in various cases
> the grouping together, namely when the bits are grouped together
> in some CPUID leaf's output) in sync is desirable, but following
> Linux to the bit doesn't always make sense. After all, some thinking
> will always be necessary when porting over patches.

Agreed.

 -- Keir

> Jan
> 



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[Xen-devel] Re: [PATCH] CPUID level 0x00000007:0 (ebx) is word 9, instea