indicium
Contributor
Contributor

Windows 8 Hyper-V

After playing around with a Win 8 guest, I tried to install Hyper-V and and it wouldn't work saying that a Hypervisor was alrady running.  So, I reread the Nested VM document and changed the type from Window 8 to Hyper-V, that solved this problem but then it won't install as is says my processor doesn't suppor SLAT.  Strange, I'm already running nested vm's, Player 5.0>ESXi 5.1>Win7.

Anybody have suggestions on how we can make this work?

Host:          Windows 7 Pro

Guests:      Windows 7 Ent     

                  Windows 8 Ent     

                  Server 2008 R2     

                  SUSE Ent  Server     

                  Linux                   

                  ESXi                     Win 7 nested

All OS's are 64 bit.

Hardware:    Thinkpad T410 Core i5, 8 GB Ram, 750 GB HD

                    VT-x and Execute Disable checked

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10 Replies
admin
Immortal
Immortal

Check to make sure that virtualized VT-x/EPT is enabled for your Hyper-V VM.  (Under Manage->VIrtual Machine Settings->Hardware->Processors.)

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jawadqazi
Contributor
Contributor

To overcome this problem you might have to check something about SLAT.

What is SLAT?

SLAT stands for "Second Level Address Translation".

Intel calls their SLAT technology EPT (Extended Page Table) . This technology was introduced in the Nehalem microarchitecture found in certain Core i7, Core i5, and Core i3 processors.

AMD, beginning with their third generation Opteron processors (code name Barcelona) support SLAT through their Rapid Virtualization Indexing (RVI) technology.

With respect to memory management, Windows Server 2008 R2 Hyper-V supports a new feature named Second Level Address Translation (SLAT). SLAT leverages AMD-V Rapid Virtualization Indexing (RVI) and Intel VT Extended Page Tables (NPT) technology to reduce the overhead incurred during virtual to physical address mapping performed for virtual machines. Through RVI or EPT respectively, AMD-V and Intel VT processors maintain address mappings and perform (in hardware) the two levels of address space translations required for each virtual machine, reducing the complexity of the Windows hypervisor and the context switches needed to manage virtual machine page faults. With SLAT, the Windows hypervisor does not need to shadow the guest operating system page mappings. The reduction in processor and memory overhead associated with SLAT improves scalability with respect to the number of virtual machines that can be concurrently executed on a single Hyper-V server. As an example, the Microsoft Remote Desktop Services (RDS) team recently blogged about performance tests conducted using an internal simulation tool on a Windows Server 2008 Terminal Services configuration running as a virtual machine on Windows Server 2008 R2 Hyper-V. The results showed that a SLAT-enabled processor platform increased the number of supported sessions by a factor of 1.6 to 2.5 when compared with a non-SLAT processor platform. Overall, Microsoft reports that with SLAT-enabled processors, the Windows hypervisor processor overhead drops from about 10% to about 2%, and reduces memory usage by about 1 MB for each virtual machine.

Although RVI is not required to support workloads running on Windows Server 2008 R2 Hyper-V, if you intend to run memory-intensive workloads like Remote Desktop Services, SQL Server, or web services, you should perform testing on SLAT-enabled platforms to determine whether or not you can gain significant performance improvements.

To find out if your processor supports SLAT, you will need to download a copy of CoreInfo from here

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admin
Immortal
Immortal

Jawad Qazi wrote:


To find out if your processor supports SLAT, you will need to download a copy of CoreInfo from here

That shouldn't be necessary, if the information in the original post is correct.  All Core i5 processors support SLAT.

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indicium
Contributor
Contributor

It wasn't checked, so I checked it and tried Hyper-V again.  It still says my processor doesn't support SLAT.

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admin
Immortal
Immortal

Please post (attach) the vmware.log file for the Hyper-V VM.

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dummyip
Contributor
Contributor

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indicium
Contributor
Contributor

Log file attached.

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admin
Immortal
Immortal

Everything looks fine from the log file.  Your physical processor supports SLAT, and the settings are correct for the virtual processor to support SLAT as well.

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indicium
Contributor
Contributor

I'm going to play around with it some more and let you know.

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indicium
Contributor
Contributor

It works!

First I tried Win Server 2008 R2 and had to upgrade the architecture from 6.5-7 to 9.0 and checked VT-x/EPT.  I did not change the type of of guest OS, left it at Server 2008 R2 x64 and Hyper-V installed fine.

Next I changed Windows 8 type from Hyper-V (unspported) to Win Server 2008 R2 x64 and started the vm, Win 8 reported that there was a hypervisor already running.  I then changed the type back to Hyper-V and restarted Win 8 and then Hyper-V would install.

Could be some wrong setting in the configuration file as I had changed the type of guest orginally from Win 8 x64 to Hyper-V and it wasn't recognized.  Tried this several time and it still wouldn't work.

I will add a vm over the wekend and see how that goes!

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