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Re: [Qemu-devel] x86 system and x86-64 system emulation


From: Antony T Curtis
Subject: Re: [Qemu-devel] x86 system and x86-64 system emulation
Date: Fri, 01 Apr 2005 20:51:42 +0100

On Fri, 2005-04-01 at 20:29 +0100, Natalia Portillo wrote:
> Hi!
> 
> I've just tested a CPU identification program I've made, under QEMU 
> (x86 and x86_64 guests).
> 
> In QEMU (x86 guest), CPU says it is a "GenuineIntel" Pentium II (family 
> 6, model 3, stepping 3), but following isn't in concordance:
> Pentium II doesn't support nor SSE nor SSE2 and as far as I know also 
> doesn't support FXSAVE/FXSTOR operands, and supports Virtual-86 Mode 
> Enhacement.
> I think that the CPU model information should be updated, or, doing as 
> VirtualPC, made it to be a "GenuineQEMU" CPU instead of a 
> "GenuineIntel".
> 
> In the QEMU (x86-64 guest), CPU says it is a monoprocessor 
> "AuthenticAMD" Athlon (family 6, model 2, stepping 3) in standard level 
> and in extended level it says it is a multiprocessor non-existent 
> "AuthenticAMD" processor (family B, model F, stepping D), and that it 
> is an enginering sample.
> 
> According to AMD64 Architecture Programmer's Manual, Volume 3, order 
> #24594, and to AMD Processor Recognition Application Note, order 
> #20734, it should inform of family F in standard and extended level, 
> and have an 8-bit brand id in the standard level or an 12-bit brand id 
> in the extended level (but not both) informing the exact model of 
> processor.
> 
> Also there is lacking emulation of 3DNow!, AMD extensions to MMX, a 
> more features that is expected every x86-64 processor have.

I don't think Intel's EM64T offering will support 3DNow! - so that would
be a very poor assumption to make, given that the two are supposed to be
largely compatible technologies.

But I would support the idea of returning some different CPUID string -
perhaps something lite "QEMUSimulate" or some other 12-character
sequence.

-- 
Antony T Curtis, BSc.                   UNIX, Linux, *BSD, Networking
address@hidden            C++, J2EE, Perl, MySQL, Apache
                                        IT Consultancy.





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