Re: [Qemu-devel] [PATCH 1/2] [RFC] Make vmport report the processor speed

[Anthony Liguori <anthony@codemonkey.ws>]

François Revol wrote:
>> If VMware ESX finds itself virtualized (read: inside VMware), 
>> it reads the TSC speed
>> from its backdoor, because measuring the TSC inside a VM is not 
>> exact.
>>
>> This patch implements a hacky way to detect the TSC speed and passes 
>> that through to
>> the VM. I am open to suggestions on how to improve the behavior.
>> It also adds a magic return value of 2 on the version return, 
>> which is required by
>> VMware ESX
>>     
>
> Oh this is interesting, I might add some stuff to Haiku to use it..
> BeOS (and Haiku) use RDTSC for timing, it's much more precise, but it's 
> why it runs so strange in VMs... (and will have to be handled when 
> implementing speedstep)
>   

You should look at KVM_CLOCK in Linux.  We could easily implement it for 
QEMU.  It provides a saner way to use the TSC as a time source in the  
guest.

Regards,

Anthony Liguori

> François.
>
>
>