On Tue, Mar 29, 2016 at 04:02:24PM +0100, Richard W.M. Jones wrote: > Back in the day you used to be able to set DEBUG_IOPORT in ioport.c > and get qemu to dump what (x86) I/O ports were being accessed by the > guest. This was rather useful for finding out what closed source > device drivers were up to. > > Now you're supposed to use cpu_in/cpu_out tracepoints instead. > However for the majority of guests these tracepoints will never be > called. > > So this patch tries to rationalize all of that. It: > > - replaces cpu_in/cpu_out with ioport_in/ioport_out tracepoints > > - moves them down in the stack, so they actually get called > > - fixes various details like address size > > It turns out this is still not particularly useful for debugging > because (a) it creates massive amounts of log messages and (b) there's > no way to select a range of addresses or a device of interest. For > example, if you have a serial port, everything else gets swamped by > I/O access to the serial port. Maybe using a different tracing > backend (eg. stap) would help? > > Anyway, it still seems to me to be an improvement over the current > situation.
I use "perf -e kvm:kvm_pio" but it's worth fixing QEMU's own trace events. Stefan
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