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Date: Mon, 14 Apr 2025 19:43:46 -0400
From: Steven Rostedt <rostedt@goodmis.org>
To: Dave Hansen <dave.hansen@intel.com>
Cc: Junxuan Liao <ljx@cs.wisc.edu>, linux-trace-kernel@vger.kernel.org,
 linux-kernel@vger.kernel.org, x86@kernel.org, Thomas Gleixner
 <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>, Borislav Petkov
 <bp@alien8.de>, Dave Hansen <dave.hansen@linux.intel.com>, "H. Peter Anvin"
 <hpa@zytor.com>, Masami Hiramatsu <mhiramat@kernel.org>, Mathieu Desnoyers
 <mathieu.desnoyers@efficios.com>, "Paul E. McKenney" <paulmck@kernel.org>
Subject: Re: [PATCH] x86/tracing: introduce enter/exit tracepoint pairs for
 page faults
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On Mon, 14 Apr 2025 16:37:19 -0700
Dave Hansen <dave.hansen@intel.com> wrote:

> On 4/14/25 16:22, Junxuan Liao wrote:
> > On 4/14/25 6:14 PM, Junxuan Liao wrote:  
> >> Do people find separate user/kernel tracepoints useful? For me, I can
> >> check regs in eBPF tracing code instead.  
> > I think it might be good to add a field to the tracepoints to indicate
> > whether it's in user space or not.  
> 
> Sounds sane to me.  Doing something like this:
> 
>         TP_STRUCT__entry(
>                 __field(                unsigned long, address  )
>                 __field(                unsigned long, ip       )
> +               __field(                bool	     , user_mode)
>                 __field(                unsigned long, error_code )
>         ),
> 
>         TP_fast_assign(
>                  __entry->address = address;
>                  __entry->ip         = regs->ip;
> +                __entry->user_mode  = user_mode(regs);
>                  __entry->error_code = error_code;
>         ),
> 
> seems highly superior to having two sets of tracepoints and static keys.

I agree.

Acked-by: Steven Rostedt (Google) <rostedt@goodmis.org>

-- Steve