Re: [PATCH v4 0/8] KVM: x86: hyperv: PV TLB flush for Windows guests

[Vitaly Kuznetsov]

Wanpeng Li <kernellwp@xxxxxxxxx> writes:

> Hi Vitaly,
> 2018-05-16 23:21 GMT+08:00 Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>:
>> Changes since v3 [Radim Krcmar]:
>> - PATCH2 fixing 'HV_GENERIC_SET_SPARCE_4K' typo added.
>> - PATCH5 introducing kvm_make_vcpus_request_mask() API added.
>> - Fix undefined behavior for hv->vp_index >= 64.
>> - Merge kvm_hv_flush_tlb() and kvm_hv_flush_tlb_ex()
>> - For -ex case preload all banks with a single kvm_read_guest().
>>
>> Description:
>>
>> This is both a new feature and a bugfix.
>>
>> Bugfix description:
>>
>> It was found that Windows 2016 guests on KVM crash when they have > 64
>> vCPUs, non-flat topology (>1 core/thread per socket; in case it has >64
>> sockets Windows just ignores vCPUs above 64) and Hyper-V enlightenments
>
> We try the below command line, the Windows 2016 guest successfully to
> login and there are 80 vCPUs can be observed in the guest w/o the
> patchset, why you mentioned the crash and ignore?
>
> /usr/local/bin/qemu-system-x86_64 -machine  pc-i440fx-rhel7.3.0  -m
> 8192 -smp 80,sockets=2,cores=40,threads=1  -device
> ide-drive,bus=ide.0,drive=test -drive
> id=test,if=none,file=/instanceimage/359b18ab-05bb-460d-9b53-89505bca68ed/359b18ab-05bb-460d-9b53-89505bca68ed_vda_1.qcow2
>  -net nic,model=virtio -net user -monitor stdio -usb -usbdevice tablet
> --enable-kvm --cpu host -vnc 0.0.0.0:2

Crash happens when you manifest yourself as Hyper-V, you can do this by
adding any 'hv-*' feature (e.g. try '-cpu host,hv_vpindex'). 

-- 
  Vitaly