On Fri, Jul 20, 2018 at 10:02:10AM +0200, Vitaly Kuznetsov wrote: > Andy Lutomirski <l...@amacapital.net> writes: > > > [I added PeterZ and Vitaly -- can you see any way in which this would > > break something obscure? I don't.] > > Thanks for CCing me, > > I don't see how this can break things either. At first glance, however, > I'm afraid we can add performance penalty to virtualized guests which > don't use native_flush_tlb_others() (Hyper-V, KVM): we will be reloading > CR3 without a need as we don't look at lazy mode in PV tlb flush > functions. > > We can either check to switch_mm_irqs_off() that > native_flush_tlb_others() is in use or teach PV tlb flush functions to > look at lazy mode too.
As Rik noted elsewhere in the thread, kvm_flush_tlb_others() ends up calling native_tlb_flush_others() for all running vcpu threads. The Hyper-V thing is magical, we can't really do anything about it there. Let them worry about it.
