Hi Ceco, I was walking Yordan down the code in the kernel to show him the ideas I have about using kvm_exit as the trace event on the host side, when I noticed that it's called *after* interrupts and preemption are enabled! This totally breaks the design, as it is not a reliable event, because the process running the guest is likely to get an interrupt or preempted before recording that event, which can cause a huge difference. kvm_enter is fine, but the reason that kvm_exit is not, is because, in order to record the reason for the exit, it needs to call into either the Intel or AMD code (as they are different), and that is done after interrupts and preemption are enabled. Instead, we can trace the function kvm_read_l1_tsc, which happens while interrupts are still enabled. Would you be able to test with that function instead of using kvm_exit? Also, if you still see a drift, try setting both trace clocks to x86-tsc, and see if you still get a drift. Thanks! -- Steve
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