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Re: [Xen-devel] [PATCH] mask cpuid TSC invariant bit for various circums

To: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>, "Xen-Devel (E-mail)" <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH] mask cpuid TSC invariant bit for various circumstances (Take 2)
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Fri, 06 Nov 2009 16:26:08 +0000
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Thread-topic: [Xen-devel] [PATCH] mask cpuid TSC invariant bit for various circumstances (Take 2)
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On 06/11/2009 14:23, "Dan Magenheimer" <dan.magenheimer@xxxxxxxxxx> wrote:

>> I think I pushed you into changing this in a way I like even
>> less. :-) I can
>> live with your original patch, so I'll check that in after all.
>>  -- Keir
> But note that you were correct that the original patch
> didn't work with HVM domains, I presume because the xc cpuid
> policy code doesn't initialize 0x80000007.  That's why
> I pulled the code out of the loop in domain_cpuid and
> then entirely out to time.c

Even if it didn't initialise 0x80000007 --- which actually I am sure it
does, as DEF_MAX_EXT is defined as 0x80000008 in xc_cpuid_x86.c --- then the
result will be we return all zeroes for that leaf. And that's safe. So I
think the original patch is fine for HVM guests too.

 -- Keir

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