What is the right CPU mask and how can I get it to my many VMs?

[KlinikenLB]

I fear this question is already answered, but I couldn't find it. So here is my qauestion:

I want to use HP DL585G2 (AMD Opteron 8220) and HP DL385G1 (AMD Opteron 285) in one cluster with the possibility of VMotion on running VMs.

So what CPU mask do I have to use on my VMs? And what is the easiest way to ditribute it to all VMs?

Thanks and regards

Dietmar

[Dave_Mishchenko]

If you're running VC 2.0.1 Patch 2 you can do it at this level instead of per VM:

>>Modifications are made at the VirtualCenter Server level but can be defined by processor manufacturer, by version number, and other criteria.

http://kb.vmware.com/selfservice/microsites/search.do?cmd=displayKC&externalId=1993

Here is the AMD doc to start with.

VMotion CPU Compatibility Requirements for AMD Processors (http://kb.vmware.com/kb/1992)

[KlinikenLB]

This KB articles are hard stuff. It's really not easy to filter out the matching informations.

If you're running VC 2.0.1 Patch 2 you can do it at

this level instead of per VM:

>>Modifications are made at the VirtualCenter Server

level but can be defined by processor manufacturer,

by version number, and other criteria.

This does not match for me. Yes, I run this VC, but this kind of modifications work with ESX 2.x. So I think I have to do it by VM.

http://kb.vmware.com/selfservice/microsites/search.do?

cmd=displayKC&externalId=1993

Here is the AMD doc to start with.

VMotion CPU Compatibility Requirements for AMD

Processors (http://kb.vmware.com/kb/1992)

Okay, it seems as I am in the AMD groups C and D. And I need the RDTSCP mask. Does this mean that I have to make this change

RDTSCP 80000001 edx -

---

0--- -

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-

---

-

---

-

---

-

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-

---

manually for every VM in my cluster?

[Texiwill · Accepted solution]

Hello,

Yes you will have to do this or write a script to do it using the SDK or vmperl.

Best regards,

Edward

[KlinikenLB]

Okay, I will think about scripting in my next three holiday weeks, and then I will try it out.

[esxfan]

problem with CPU compatibility discussed at http://www.vmware.com/community/message.jspa?messageID=508886#636800

DL585 G1 and DL385 G1 should have same CPU type.

I uses -

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0-0- -

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-

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-

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-

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-

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---0 too and it works fine for me (we have DL585 G1, DL585 G2 and DL585 G2)

CU

esxfan

[KlinikenLB]

But in the VMware article

http://kb.vmware.com/selfservice/microsites/search.do?cmd=displayKC&externalId=1993

they say that you only need to change the RDTSCP mask (if I understood it correct this means to change RDTSCP 80000001 edx -

---

0--- -

---

-

---

-

---

-

---

-

---

-

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)

Why did you change to -

---

0-0- -

---

-

---

-

---

-

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-

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---0 ? (the first 0 is RDTSCP, the second 0 is FFXSR, but for what is the 0 at the end?)

Regards, Dietmar

P.S.: I have DL385G1 and DL585G2, this means different CPU types

[KlinikenLB]

Now my experience:

I put the mask RDTSCP 80000001 edx -

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0--- -

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-

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-

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-

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-

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-

---

to all my VMs (W2kServer, W2003Server EE and Standard, WinXP SP2, Ubuntu, Debian, SLES) and they all migrated fine in both directions.

But attention:

Many forum threads (and also the KB articles) let you think that the CPU mask works as a mask between the CPU and the VM. And the guest OS sees a masked CPU. This is not true \!!!

Meanwhile I found out that the CPU mask does not work between the CPU and the VM. The CPU mask only works for the Vmotion compatibility check![/b] The CPU mask hides the feature only to the compatibility check but not to the VM (Reason: the CPU is a socalled passthrough device for the VM)

This means: with a CPU mask Vmotion will migrate the VM unless the guest OS in the VM matches to the new CPU or not

Regards, Dietmar