On 30/05/19 21:36, Sean Christopherson wrote: >> +u32 __read_mostly vmentry_lapic_timer_advance_ns = 0; >> +module_param(vmentry_lapic_timer_advance_ns, uint, S_IRUGO | S_IWUSR); > Hmm, an interesting idea would be to have some way to "lock" this param, > e.g. setting bit 0 locks the param. That would allow KVM to calculate the > cycles value to avoid the function call and the MUL+DIV. If I'm not > mistaken, vcpu->arch.virtual_tsc_khz is set only in kvm_set_tsc_khz(). I would just make it read-only. But I'm afraid we're entering somewhat dangerous territory. There is a risk that the guest ends up entering the interrupt handler before the TSC deadline has actually expired, and there would be no way to know what would happen; even guest hangs are possible. Paolo
