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

[Yan Vugenfirer <yvugenfi@redhat.com>]

Hi,

First off all to use more than 64 CPUs on Windows you should use CPU grouping. Each group can contain maximum 64 CPUs. Here is a good article explaining possible configurations:
https://msdn.microsoft.com/en-us/windows/hardware/drivers/devtest/boot-parameters-to-test-drivers-for-multiple-processor-group-support <https://msdn.microsoft.com/en-us/windows/hardware/drivers/devtest/boot-parameters-to-test-drivers-for-multiple-processor-group-support> and another one on the grouping subject: https://blogs.technet.microsoft.com/mlucas/2012/03/15/windows-server-and-processor-cores/ <https://blogs.technet.microsoft.com/mlucas/2012/03/15/windows-server-and-processor-cores/>

Regarding the boot failure - it is quite possible that Windows cannot handle more that 64 logical CPUs on one physical CPU. 

Best regards,
Yan.
> On 9 Feb 2017, at 08:18, hangaohuai <hangaohuai@huawei.com> wrote:
> 
> Dear all:
> I try to boot windows2012R2 (more than 64 cores)on kvm platform with hyper-v on*<relaxed state='on'/>*.
> the guest halts on the starting time.
> Also tested in these cases:
> <topology sockets='64' cores='1' threads='1'/>  - boot sucess
> <topology sockets='1' cores='64' threads='1'/>  - boot sucess
> <topology sockets='1' cores='1' threads='64'/>  - boot sucess
> <topology sockets='1' cores='68' threads='1'/>  - boot failed
> <topology sockets='68' cores='1' threads='1'/>  - boot sucess(in Guest we can found 64)
> <topology sockets='1' cores='1' threads='68'/>  - boot failed
> 
> Environment:
> GUEST:
>  windows2012R2
> HOST:
>    kernel version:4.10.0-rc4
>    QEMU version:QEMU emulator version 2.8.50 (v2.8.0-664-gd1c82f7-dirty)
> part of GuestXML:
>  <vcpu placement='static'>68</vcpu>
>  <resource>
>    <partition>/machine</partition>
>  </resource>
>  <os>
>    <type arch='x86_64' machine='pc-i440fx-2.3'>hvm</type>
>    <boot dev='hd'/>
>  </os>
>  <features>
>    <acpi/>
>    <apic/>
>    <pae/>
>    <hyperv>
>      <relaxed state='on'/>
>    </hyperv>
>  </features>
>  <cpu>
>    <topology sockets='1' cores='68' threads='1'/>
>  </cpu>
> 
> //////////////////////////////////
> debug info:
> virsh qemu-monitor-command win2012 --hmp "info cpus"
>  CPU #61: pc=0xfffff8031296a21c thread_id=21410
>  CPU #62: pc=0xfffff8031296a21c thread_id=21411
>  CPU #63: pc=0xfffff8031296a21c thread_id=21414
>  CPU #64: pc=0x00000000000fd31c (halted) thread_id=21415
>  CPU #65: pc=0x00000000000fd31c (halted) thread_id=21416
>  CPU #66: pc=0x00000000000fd31c (halted) thread_id=21417
>  CPU #67: pc=0x00000000000fd31c (halted) thread_id=21418
> 
> 
> Any suggestions?
> 
> Thanks a lot.
> 
> Gaohuai Han
> 
>