On Tue, Oct 04, 2016 at 03:29:33PM +1100, Michael Ellerman wrote: > Peter Zijlstra <[email protected]> writes: > > So it would be good to also explain why PPC needs this in the first > > place. > > Unfortunately I don't really know the code, and the original author is AWOL. > > But AFAICS perf_event_disable() is only called here: > > if (!stepped) { > WARN(1, "Unable to handle hardware breakpoint. Breakpoint at " > "0x%lx will be disabled.", info->address); > perf_event_disable(bp); > goto out; > } > > Which is where we cope with the possibility that we couldn't emulate the > instruction that hit the breakpoint. Seems that is not an issue on x86, > or it's handled elsewhere?
I don't think x86 ever needs to emulate things on hw breakpoint (although I could be mistaken), but I would expect ARM to maybe need so, and I couldn't find a disable there either. Will? > We should fix emulate_step() if it failed to emulate something it > should have, but there will always be the possibility that it fails. > > Instead of calling perf_event_disable() we could just add a flag to > arch_hw_breakpoint that says we hit an error on the event, and block > reinstalling it in arch_install_hw_breakpoint(). Possible..
