Re: Linux in VirtualPC in KVM fails

Anthony Liguori
2009-01-09T19:04:23Z

Alexander Graf wrote:
>
> Shouldn't it be ok to push patches to linux-stable to use the CPUID
> and MSR information and simply not expose the CPUID identification in
> newer KVM versions? That way older guests on newer KVM don't use KVM
> paravirt (which should still be ok), but everything else runs as
> smoothly as possible.

I'd say that VirtualPC is broken and leave it at that.

All modern hypervisors use CPUID to expose themselves to the guests.
VirtualPC is totally capable of rewriting CPUID instructions. Shame on
it for not doing so. I don't think we should change anything.

Regards,

Anthony Liguori

> Alex
>
>> So I suggest:
>> - add a new cpuid bit, for 'paravirt verification'
>> - if the new bit is present, the guest verifies that paravirt is
>> truly enabled by reading an msr (and checking a signature).
>>
>> Older guests or newer guests running on older hosts will still be
>> broken, but there's a command line parameter for disabling paravirt
>> on the guest, and we can add one for the host as well.
>>
>> --
>> I have a truly marvellous patch that fixes the bug which this
>> signature is too narrow to contain.
>>
>
> --
> To unsubscribe from this list: send the line "unsubscribe kvm" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html