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


From: Anthony Liguori
Subject: Re: [Qemu-devel] [PATCH 1/2] [RFC] Make vmport report the processor speed
Date: Mon, 05 Jan 2009 22:56:48 -0600
User-agent: Thunderbird 2.0.0.14 (X11/20080421)

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.







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