Re: [Qemu-devel] [Help] Windows2012 as Guest 64+cores on KVM Halts

[Paolo Bonzini <pbonzini@redhat.com>]

On 20/02/2017 10:19, Gonglei (Arei) wrote:
> Hi Paolo,
> 
>>
>>
>> On 16/02/2017 02:31, Gonglei (Arei) wrote:
>>> And the below patch works for me, I can support max 255 vcpus for WS2012
>>> with hyper-v enlightenments.
>>>
>>> diff --git a/target/i386/kvm.c b/target/i386/kvm.c
>>> index 27fd050..efe3cbc 100644
>>> --- a/target/i386/kvm.c
>>> +++ b/target/i386/kvm.c
>>> @@ -772,7 +772,7 @@ int kvm_arch_init_vcpu(CPUState *cs)
>>>
>>>          c = &cpuid_data.entries[cpuid_i++];
>>>          c->function = HYPERV_CPUID_IMPLEMENT_LIMITS;
>>> -        c->eax = 0x40;
>>> +        c->eax = -1;
>>>          c->ebx = 0x40;
>>>
>>>          kvm_base = KVM_CPUID_SIGNATURE_NEXT;
>>
>> This needs to depend on the machine type, but apart from that I think
> 
> I don't know why. Because the negative effects for this change don't exist
> on current QEMU IIUC, and we don't have compatible problems for live migration.

CPUID should never change with the same machine type and command line.

Paolo

>> you should submit the patch for 2.9.
>>
> 
> Thanks,
> -Gonglei
>