Peter Maydell <[email protected]> writes: > On 7 November 2018 at 17:39, Peter Maydell <[email protected]> wrote: >> On 7 November 2018 at 17:10, Alex Bennée <[email protected]> wrote: >>> Not all faults handled by handle_exit are instruction emulations. For >>> example a ESR_ELx_EC_IABT will result in the page tables being updated >>> but the instruction that triggered the fault hasn't actually executed >>> yet. We use the simple heuristic of checking for a changed PC before >>> seeing if kvm_arm_handle_step_debug wants to claim we stepped an >>> instruction. >>> >>> Signed-off-by: Alex Bennée <[email protected]> >> >> What's the rationale for this change? Presumably it's fixing >> something, but the commit message doesn't really say what... >> >> This feels to me like it's working around the fact that >> we've separated two things ("advance pc (or set it if we're >> going to make the guest take an exception)" and "notice that >> we have completed a single step") that should be handled >> at one point in the code. > > ...so for instance if your guest PC is at the entrypoint for > an exception, and you singlestep and take the same exception > again, this should count as a single step completed, even > though the PC has not changed. Granted, that's a little > contrived, but it can happen in cases where the guest gets > completely confused and is sitting in a tight loop taking > exceptions because there's no ram at the vector table > address, or whatever.
The alternative I thought of as I was hacking^H^H^H^H^H^H carefully engineering this was to expand arm_exit_handlers[] and tag each handler that was an instruction emulation and gate on that. -- Alex Bennée _______________________________________________ kvmarm mailing list [email protected] https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
