Re: [Qemu-devel] [Bug Report] vm paused after succeeding to migrate

[linzhecheng]

> -----邮件原件-----
> 发件人: Dr. David Alan Gilbert [mailto:address@hidden
> 发送时间: 2018年4月12日 20:37
> 收件人: linzhecheng <address@hidden>; address@hidden
> 抄送: address@hidden; wangxin (U) <address@hidden>;
> Zhoujian (jay) <address@hidden>; address@hidden
> 主题: Re: [Qemu-devel] [Bug Report] vm paused after succeeding to migrate
> 
> * linzhecheng (address@hidden) wrote:
> > Hi, all
> > I encounterd a bug when I try to migrate a windows vm.
> >
> > Enviroment information:
> > host A: cpu E5620(model WestmereEP without flag xsave) host B: cpu
> > E5-2643(model SandyBridgeEP with xsave)
> >
> > The reproduce steps is :
> > 1. Start a windows 2008 vm with -cpu host(which means host-passthrough).
> > 2. Migrate the vm to host B when cr4.OSXSAVE=0 (successfully).
> > 3. Vm runs on host B for a while so that cr4.OSXSAVE changes to 1.
> > 4. Then migrate the vm to host A (successfully), but vm was paused, and
> qemu printed log as followed:
> 
> Remember that migrating using -cpu host  across different CPU models is NOT
> expected to work.
> 
> > KVM: entry failed, hardware error 0x80000021
> >
> > If you're running a guest on an Intel machine without unrestricted
> > mode support, the failure can be most likely due to the guest entering
> > an invalid state for Intel VT. For example, the guest maybe running in
> > big real mode which is not supported on less recent Intel processors.
> >
> > EAX=019b3bb0 EBX=01a3ae80 ECX=01a61ce8 EDX=00000000
> > ESI=01a62000 EDI=00000000 EBP=00000000 ESP=01718b20
> > EIP=0185d982 EFL=00000286 [--S--P-] CPL=0 II=0 A20=1 SMM=0 HLT=0 ES
> > =0000 00000000 0000ffff 00009300 CS =f000 ffff0000 0000ffff 00009b00
> > SS =0000 00000000 0000ffff 00009300 DS =0000 00000000 0000ffff
> > 00009300 FS =0000 00000000 0000ffff 00009300 GS =0000 00000000
> > 0000ffff 00009300
> > LDT=0000 00000000 0000ffff 00008200
> > TR =0000 00000000 0000ffff 00008b00
> > GDT=     00000000 0000ffff
> > IDT=     00000000 0000ffff
> > CR0=60000010 CR2=00000000 CR3=00000000 CR4=00000000
> > DR0=0000000000000000 DR1=0000000000000000 DR2=0000000000000000
> > DR3=0000000000000000
> > DR6=00000000ffff0ff0 DR7=0000000000000400
> > EFER=0000000000000000
> > Code=00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 <00>
> > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> > 00 00 00 00 00 00
> >
> > I have found that problem happened when kvm_put_sregs returns err -
> 22(called by kvm_arch_put_registers(qemu)).
> > Because kvm_arch_vcpu_ioctl_set_sregs(kvm-mod) checked that
> guest_cpuid_has no X86_FEATURE_XSAVE but cr4.OSXSAVE=1.
> > So should we cancel migration when kvm_arch_put_registers returns error?
> 
> It would seem good if we can make the migration fail there rather than hitting
> that KVM error.
> It looks like we need to do a bit of plumbing to convert the places that call 
> it to
> return a bool rather than void.
I think we should return a int value of run_on_cpu which callback 
run_on_cpu_func, but run_on_cpu_func is the prototype of many functions,
Is it overkill?
> 
> Dave
> 
> --
> Dr. David Alan Gilbert / address@hidden / Manchester, UK