Re: [Qemu-devel] [PATCH RFC v1 2/2] hyper-v: initialize Hyper-V CPUID leafs.

[Paolo Bonzini]

On 10/17/2011 11:17 AM, Vadim Rozenfeld wrote:
> @@ -379,11 +380,16 @@ int kvm_arch_init_vcpu(CPUState *env)
>       cpuid_i = 0;
>
>       /* Paravirtualization CPUIDs */
> -    memcpy(signature, "KVMKVMKVM\0\0\0", 12);
>       c =&cpuid_data.entries[cpuid_i++];
>       memset(c, 0, sizeof(*c));
>       c->function = KVM_CPUID_SIGNATURE;
> -    c->eax = 0;
> +    if (!hyperv_enabled()) {
> +        memcpy(signature, "KVMKVMKVM\0\0\0", 12);
> +        c->eax = 0;
> +    } else {
> +        memcpy(signature, "Microsoft Hv", 12);
> +        c->eax = HYPERV_CPUID_MIN;
> +    }

Even not counting that hyper-v support should IMHO not be in 
KVM-specific code, I still think this shouldn't remove KVM leaves 
completely but rather move them to 0x40000100.  The KVM 
paravirtualization code then can similarly probe with 0x100 stride up to 
0x40001000.  This is what was done for Xen, and it allows to enable 
enlightenments independent of whether the guest is Linux or Windows.

However, let's get a third opinion---Avi, what do you think?

Paolo