RE: [Xen-devel] A simple question of CPU emulation in Xen

[MaoXiaoyun <tinnycloud@xxxxxxxxxxx>]

 
> Subject: RE: [Xen-devel] A simple question of CPU emulation in Xen
> Date: Mon, 16 May 2011 11:46:26 +1000
> From: james.harper@xxxxxxxxxxxxxxxx
> To: tinnycloud@xxxxxxxxxxx
> CC: xen-devel@xxxxxxxxxxxxxxxxxxx
>
> >
> > 在 2011-5-14，7:41，"James Harper" <james.harper@xxxxxxxxxxxxxxxx> 写道：
> >
> > >> Hi :
> > >>
> > >> I have a simple question on CPU emulation in Xen.
> > >>
> > >> Currently, inside guest, we can see that the CPU information
> > > incluing
> > >> types and frequency is exactly
> > >> same as physical CPU. Is it possible for Xen(or qemu) to emulate a
> > > different
> > >> type of CPU. That is inside
> > >> guest, we see a different CPU types?
> > >>
> > >> If it is possible, could someone elighten me where to start.
> > >>
> > >
> > > Do you want to emulate a completely different platform (eg PPC / alpha /
> > > Sparc) or just pretend the cpu is a slightly different flavours (eg
> > > running a late model Xeon CPU but emulate a P2)?
> > >
> > Thanks, exactly what I want.
> > since cpus are shared along All VMs, so In guest, youn will get lower score if
> > we make tests
> > with Xeon. While higher score is it is pretend to be P2.
> > > In a lot of cases you can do the latter by changing some CPUID values in
> > > the DomU config to mask the CPU features so the guest thinks it is
> > > running on an older model.
> >
> > Could i have the configuration u refer to? In hvm file?
> > Thanks
> >
>
> I did something like this to give my DomU the lowest common feature set between my AMD and Intel based servers for live migration:
>
> cpuid = [ '0:eax=0x3,ebx=0x0,ecx=0x0,edx=0x0',
> '1:eax=0x06b1,ecx=xxxxxxxxxxx0000xx00xxx0000000xx0,edx=xxx00000xxxxxxx0xxxxxxxxx0xxxxxx',
> '4:eax=0x3,ebx=0x0,ecx=0x0,edx=0x0',
> '0x80000000:eax=0x3,ebx=0x0,ecx=0x0,edx=0x0']
>
> But I haven't tried it in a while so I can't tell if it still works as it should. I do know that Silverlight won't install with the above because it requires some feature that I've masked out.
>
> There are some other examples in the example configs I think.
 
I've tried a little bit, it still works.
I'll take a look CPUID configuration in detail myself.
Many thanks.
>
> James

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