[Qemu-devel] Starting KVM/VMX guest with non-exiting RDTSC instruction

[Lluís Vilanova]

Hi,

Is there some way to start a KVM-accelerated VM with QEMU (on an Intel/VMX
host) that is configured so that RDTSC/RDTSCP instructions won't cause a
VM-exit?

According to Intel's manual, it seems I should disable the "RDTSC exiting"
bit on the MSR that Linux identifies as MSR_IA32_VMX_PROCBASED_CTLS (in its
KVM code).

I've checked the vmxcap script from qemu:

$ sudo /tmp/vmvm-vilanova/vmxcap.py | grep -i rdtsc
  RDTSC exiting                            yes
  Enable RDTSCP                            yes

So, can I somehow curbe QEMU+KVM to disable RDTSC exiting?

Thanks,
Lluis