Re: [Xen-devel] Why "Mask cmpxchg8b capability in cpuid for non-

To:	"Cui, Dexuan" <dexuan.cui@xxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>, <Tim.Deegan@xxxxxxxxxxxxx>
Subject:	Re: [Xen-devel] Why "Mask cmpxchg8b capability in cpuid for non-pae guests"?
From:	Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date:	Thu, 28 Dec 2006 10:02:49 +0000
Cc:	"Huang, Xinmei" <xinmei.huang@xxxxxxxxx>
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On 28/12/06 9:55 am, "Cui, Dexuan" <dexuan.cui@xxxxxxxxx> wrote:

> I noticed you "Mask cmpxchg8b capability in cpuid for non-pae guests" in
> changeset 13107/13108: clear_bit(X86_FEATURE_CX8 & 31, edx). May I know
> the reason for the change?

It's needed to successfully install NT4, which has a bug in older service
packs where it barfs on the CMPXCHG8B feature bit in CPUID. The right 'fix'
is to allow arbitrary masking of CPUID features in the guest config file.
We'll revert this workaround.

 Thanks,
 Keir

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Re: [Xen-devel] Why "Mask cmpxchg8b capability in cpuid for non-pae gues