[Xen-devel] Changing the CPUID hypervisor string for HVM DomU

[Fanny Dwargee <fdwargee6@xxxxxxxxx>]

Hi,

I'm currently using Xen v4.6.1 compiled from sources on Linux Debian Jessie and I would like to change the CPUID hypervisor vendor string when queried from a HVM DomU (Windows7 SP1 64 bits).

According to http://www.sandpile.org/x86/cpuid.htm#level_4000_0000h this information is queried via EAX=0x40000000 and returned on EBX-ECX-EDX registers

The current vendor string is "XenVMMXenVMM" and I want to replace it by the string "JUSTATEST" so I changed my DomU configuration to:

[...]

cpuid = [ '0x40000000:eax=xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx,ebx=01010100010100110101010101001010,ecx=00000000000000000000000001010100,edx=01010011010001010101010001000001' ]

hap  = 1

acpi = 1

altp2mhvm = 1

[...]

but unfortunately the guest still shows "XenVMMXenVMM" as the hypervisor string.

After looking for that string in the Xen sources it seems to be harcoded in many places:

• xen-4.6.1/docs/misc/pvrdtscp.c
  
• xen-4.6.1/tools/firmware/seabios-dir-remote/src/fw/xen.c
  
• xen-4.6.1/tools/firmware/hvmloader/hvmloader.c
  
• xen-4.6.1/tools/misc/xen-detect.c
  
• xen-4.6.1/unmodified_drivers/linux-2.6/platform-pci/platform-pci.c
  
• xen-4.6.1/xen/include/public/arch-x86/cpuid.h
  
• xen-4.6.1/extras/mini-os/include/xen/arch-x86/cpuid.h
  
• xen-4.6.1/dist/install/usr/local/include/xen/arch-x86/cpuid.h
  

...so I'm afraid I will be unable to change it.

Any ideas or patches?

Thanks in advance

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