Re: [Xen-devel] Question about XEN Hypervisor MSR capability exposion to VMs

["Zhang, Yang Z" <yang.z.zhang@xxxxxxxxx>]

Liuyingdong wrote on 2015-10-31:
> Hi All
> 
> We encountered a blue screen problem when live migrate
> Win8.1/Win2012R2 64bit VM from V3 processor to non-V3 processor
> sandbox, KVM does not has this problem.
> 
> After looking into the MSR capabilities, we found XEN hypervisor
> exposed bit 39 and bit 18 to the VM, from Intel manual bit 39 refers
> to reserve bit and should not be set, bit 18 refers to MWAIT/MONITOR

Reserved doesn't mean it must be zero or one. Can you help to check it on host?

> capability, from my understanding it should not exposed to the VM too.

Yes, the MWAIT/MONITOR should be hidden from guest.

> BTW, KVM does not expose bit 18/39 to the VM.
> 
> Below is the boot message: (XEN) read msr: ecx=c0000083,
> msr_value=0xfffff80028ddf240 (XEN) read msr: ecx=1a0,
> msr_value=0x4000801889
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ (XEN)
> write msr:msr=40000071, msr_value=0x10000000000082f (XEN) write
> msr:msr=40000070, msr_value=0x0 (XEN) write msr:msr=40000071,
> msr_value=0x20000000000082f (XEN) write msr:msr=40000070, msr_value=0x0
> (XEN) read msr: ecx=17, msr_value=0x0 (XEN) write msr:msr=8b,
> msr_value=0x0 (XEN) read msr: ecx=8b, msr_value=0x2d00000000



Best regards,
Yang



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