Re: [RFC] Expose host cpuid to guest

[Mike Lampard <mike-/+b+wjvSUqIxsqv6Oivclw@public.gmane.org>]

On Wed, 21 Nov 2007 09:36:31 pm Dan Kenigsberg wrote:
> These patches expose host CPU features (that are known to work under
> KVM) to guests. It makes a couple of benchmarks run faster, and
> generally gives kvm's user better info on its host.
>
> The kernel-space patch adds KVM_GET_SUPPORTED_CPUID ioctl to obtain the
> table of cpuid functions supported by the host. The user-space patch
> allows fine-tuning this table from the command-line.
>
> I had to define struct kvm_cpuid2, KVM_SET_CPUID2 etc., because cpuid
> functions are a little more complex than just function-value pairs.
>
> Dan.

With current kvm-git (commit 51727a110220681f6f43b005d069e28c58f5d151) 
(userspace is current to commit 6a385c9539f9746d7ff51ef34c064c3eba86448b) and 
the userspace portion of this patch I cannot boot a 64 bit guest (Mandriva 
2008 x64) on my AMD x2 without -cpu host.  The guest kernel says "Your CPU 
does not support long mode.  Use a 32bit distribution.".  Works fine without 
the userspace portion of the patch.  

With -cpu host, the 64bit kernel starts to boot then panics almost 
immediately:
Code: 0f 30 e9 ed fc ff ff b8 66 00 00 00 f0 0f ab 45 08 e9 e2 fa
RIP [<ffffffff8020ff99> identify_cpu+0x609/0x700
 RSP <ffffffff8057df58>
Kernel panic - not syncing: Attempted to kill the idle task!

In the host log I see: cpu0 unhandled wrmsr: 0xc0010015, which might not have 
anything to do with this patch of course :)

Mike

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