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On 4/14/25 4:56 PM, Dave Hansen wrote: > On 4/14/25 13:52, Junxuan Liao wrote: >> On 4/14/25 3:42 PM, Dave Hansen wrote: >>> Is there a reason kprobes don't work for this? >> >> In this code path it's either noinstr or inline functions, so I believe >> explicit tracepoints are necessary? > > It'd be great to turn this "??" into some more certainty. ;) > >> As Steven has mentioned, there are similar tracepoints for irq and it's >> nice to have them for page faults too. > > So, that code is: > >> trace_irq_handler_entry(irq, action); >> res = action->handler(irq, action->dev_id); >> trace_irq_handler_exit(irq, action, res); > > ... I think. > > That's a heck of a lot simpler than a couple static keys and new > conditionals. > > Also, I honestly don't think we need separate user and kernel fault > trace points. Maybe we should just zap that in the process. > > Is there a reason we couldn't get this down to something dirt simple like: > > DEFINE_IDTENTRY_RAW_ERRORCODE(exc_page_fault) > { > instrumentation_begin(); > + trace_page_fault_entry(...); > handle_page_fault(regs, error_code, address); > + trace_page_fault_exit(...); > instrumentation_end(); > > ?? If we don't need to separate user and kernel tracepoints, we won't need those static keys anyway, and it's indeed much simpler. Do people find separate user/kernel tracepoints useful? For me, I can check regs in eBPF tracing code instead. Junxuan