vMario156
Expert
Expert

Manipulating Guest CPUID

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Hi there,

I wish all a happy new year!

Did anybody ever tried to manipulate the CPUID, which is shown to the guest OS?

I have the following scenario:


CPUID shown in the guest OS: 0FABFBFF00020651
 

vmx-File Parameters:
 

guestCPUID.0 = "0000000b756e65476c65746e49656e69"
guestCPUID.1 = "0002065100010800829822030fabfbff"
 
As you can see I find the ID shown above splitted in two parts inside of the value of guestCPUID.1 (marked in bold).
 
 
I need to change this ID to 0FEBFBFF000006F1
If I manipulate the guestCPUID.1 value according to the ID I need I get the following result: After PowerOn the VM again the value gets instantly overwritten by the original value.  

I assume that the other part of the value and maybe also guestCPUID.0 are also related in some way.


Unfortunally I can´t find anything in the documation / google about this paramaters.


Thanks for any help!

Cheers,

Mario
 

 

Blog: http://vKnowledge.net
1 Solution

Accepted Solutions
admin
Immortal
Immortal

0FEBFBFF000006F1 looks like CPUID.1.EDX concatenated with CPUID.1.EAX.  So, you want CPUID.1.EDX to be 0FEBFBFF and CPUID.1.EAX to be 000006F1.  Use a binary calculator to convert hexadecimal to binary, and you get:


cpuid.1.edx = "00001111111010111111101111111111"

cpuid.1.eax = "00000000000000000000011011110001"


The only thing that would concern me is that you are changing bit 22 of CPUID.1.EDX from 0 to 1.  This will result in the virtual CPU claiming support for a feature that it does not really support, namely "ACPI." Intel documents this feature bit as follows:

Thermal Monitor and Software Controlled Clock Facilities. The processor implements internal MSRs that allow processor temperature to be monitored and processor performance to be modulated in predefined duty cycles under software control.


This may or may not be a problem, depending on what the guest OS does with these MSRs.

The guestCPUID.1 value is informational only.  You should see that value change after you have powered on the VM with the configuration options above.

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18 Replies
admin
Immortal
Immortal

Many cpuid leaves can be modified using options like the following:

# Northwood

cpuid.1.eax="----:0000:0000:0000:----:1111:0010:1001"

The general form is cpuid.<eax-in>.<gpr>="<value>"

The GPR is eax, ebx, ecx, or edx.  The colons are optional.  Ones and zeroes override the default settings, bit by bit.  Dashes are used to leave the default settings alone.

Thanks,

--jim

vMario156
Expert
Expert

Hi Jim,

thanks for you respose!

Do have any more information how I convert my desired 16-digits long CPUID (0FEBFBFF000006F1) into the correct values for cpuid.1.eax/ebx/.... ??

Whats about the guestCPUID.1 value? Isn´t it related to this ID,because I find the ID in this value (splittet into two parts), which I see inside of the OS?

Many thanks!!!
Mario

Blog: http://vKnowledge.net
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admin
Immortal
Immortal

0FEBFBFF000006F1 looks like CPUID.1.EDX concatenated with CPUID.1.EAX.  So, you want CPUID.1.EDX to be 0FEBFBFF and CPUID.1.EAX to be 000006F1.  Use a binary calculator to convert hexadecimal to binary, and you get:


cpuid.1.edx = "00001111111010111111101111111111"

cpuid.1.eax = "00000000000000000000011011110001"


The only thing that would concern me is that you are changing bit 22 of CPUID.1.EDX from 0 to 1.  This will result in the virtual CPU claiming support for a feature that it does not really support, namely "ACPI." Intel documents this feature bit as follows:

Thermal Monitor and Software Controlled Clock Facilities. The processor implements internal MSRs that allow processor temperature to be monitored and processor performance to be modulated in predefined duty cycles under software control.


This may or may not be a problem, depending on what the guest OS does with these MSRs.

The guestCPUID.1 value is informational only.  You should see that value change after you have powered on the VM with the configuration options above.

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vMario156
Expert
Expert

Awesome, worked like a charm!

Thank you very much!!

Cheers,

Mario

Blog: http://vKnowledge.net
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raffic_ncc
Enthusiast
Enthusiast

Thanks a lot....

Mohammed Raffic VCP4,VCP5,VCAP4-DCA,VCAP5-DCA,VCP-Cloud, MCSA.MCTS,CCA http://www.vmwarearena.com
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amircsco
Enthusiast
Enthusiast

thats was really helpfull mattson

you explainen about guestCPUID.1 value but there is another CPUID with this flag: guestCPUID.0

this is totally different to guestCPUID.1, so what is that??

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admin
Immortal
Immortal

guestCPUID.0 is the data from CPUID function 0, which is not all that interesting.  The first 8 hexadecimal digits indicate the maximum input value for basic CPUID Information.  The rest is the string "GenuineIntel" in a strange order (see http://www.intel.com/content/dam/www/public/us/en/documents/manuals/64-ia-32-architectures-software-... for more details). 

amircsco
Enthusiast
Enthusiast

is it possible to change it with the same way that we use for changing guestCPUID.0 ??

beside, as i know in addition of EAX and EDX there are tow other IDs covered in guestCPUID.0, they are ECX and EBX right??

how can i extract them?? is it possible to change them like EAX and EDX with adding these items for example to vmx file of virtual machine:

cpuid.1.eax = "00001111111010111111101111111111"

cpuid.1.ebx = "00000000000000000000011011110001"

Best Regards,

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admin
Immortal
Immortal

Each CPUID function populates four general purpose registers with data.  These registers are eax, ebx, ecx, and edx.  For the functions that VMware hypervisors typically mask, like function 1, it is sufficient to add a configuration entry like the ones you have indicated above.  However, if we do not typically mask the particular CPUID function you are interested in, then you will also need the option:

monitor_control.enable_fullcpuid = TRUE

As for extracting the results, you can write a program to query the CPUID function(s) of interest, or you can just look in the vmware.log file of any VM.  All current VMware hypervisors log all CPUID information for both the host and the guest

akkihere
Contributor
Contributor

Hi,

I have been trying to install mac os 10.8.2 using souldev teams tutorial, in vmware.

I have used hardware bypass software in download (vmware patch) and still it shows the same error.

I also tried to add the "cpuid" code line in .vmx file and no result.

cpu- amd athlon

asus motherboard

4gb ram

windows 7 ultimate 64 bit

tried with several versions of vmware (8,9 series) and same error every where

I have been searching for the solutions since weeks and no result.

PLEASE some body help me out guys.

Thanks advance.

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admin
Immortal
Immortal

Apple's EULA does not permit the installation of Mac OS X on non-Apple branded hardware.

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sWORDs
VMware Employee
VMware Employee

What would be needed in the vmx file to modify guestCPUID 80000002-80000005 for all vCPU's?

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admin
Immortal
Immortal

For current VMware product releases, you can modify CPUID leaves 80000002 - 80000004 with the following configuration option:

cpuid.brandstring = "whatever you want"

For example,

cpuid.brandstring = "Intel(R) Xeon(R) CPU E3-1270 v3 @ 3.50GHz"

MelodicForce
Contributor
Contributor

Hi jmattson,

you need to close the virtual machine to do that. otherwise the change does not take place.

That's what I want to learn;

Is there a program we can do without shutting down the computer?

Thanks..

xairosk
Contributor
Contributor

Yes, I need this method.

Without turning off the computer, is there a way to change BrandString?

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sWORDs
VMware Employee
VMware Employee

There is no way to reflect that to the guest os whitout a VM restart, if you vMotion you will also see the booted CPUID.

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jfo9661
Contributor
Contributor

Does anyone know if this is still available in Workstation 16 pro?   Or has implementation changed?

Having issue with move from version 15 to 16.  Workstation reports vmx is invalid when options are in place. 

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scott28tt
VMware Employee
VMware Employee

What is your use case?


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