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

[Wanpeng Li]

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

Regards,
Wanpeng Li