On Mon, Mar 25, 2019 at 10:35:28AM +0100, David Hildenbrand wrote: > On 21.03.19 23:52, Steve Rutherford wrote: > > Not that I know of. > > > > This is surprisingly hard to implement correctly in KVM. On Intel x86 > > it could be done with MTF (monitor trap fault), but you would need to > > VMEXIT at each instruction boundary, and getting the behavior right > > for other traps/faults is pretty hard when running around with MTF > > enabled on every instruction. It could be done somewhat inaccurately > > using perf counters (setup interrupt on overflow for the per-thread > > instruction count, and set the base value for that counter really > > high), but I'm not even sure what the current state of KVM's Perf > > support is, or if this trick would work well in practice since this > > isn't really what perf counters were built for. > > > > > > > > On Wed, Mar 20, 2019 at 9:33 PM liushuyu <liushuyu@xxxxxxx> wrote: > >> > >> Hi there, > >> > >> I am new to KVM API and I have a question: Is there a way to stop/kick vCPU > >> after it executes a specific number of instructions? I have searched online, > >> read the documentation in the Linux kernel source code, searched through the > >> archives of this mailing list and I couldn't find the answer. > >> > >> Thanks very much for your attention. > > There is a very hacky way to stop/kick a VCPU on every branch using the > BTS buffer and EPT, however it requires guest interaction. Most probably > not what you are looking for. Out of curiosity, why not do EFLAGS.TF=1 && MSR_IA32_DEBUGCTLMSR.BTF=1 (and VM-Exit on #DBs) to stop on branches?
