linux-kernel - Re: Question about the ipi_raise filter usage and output

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Message-ID: <20240205080609.563df00f@rorschach.local.home>
Date: Mon, 5 Feb 2024 08:06:09 -0500
From: Steven Rostedt <rostedt@...dmis.org>
To: Mark Rutland <mark.rutland@....com>
Cc: richard clark <richard.xnu.clark@...il.com>, nico@...xnic.net,
 mhiramat@...nel.org, linux-arm-kernel@...ts.infradead.org,
 linux-trace-kernel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: Question about the ipi_raise filter usage and output

On Mon, 5 Feb 2024 10:28:57 +0000
Mark Rutland <mark.rutland@....com> wrote:

> > I try to write below:
> > echo 'target_cpus == 11 && reason == "Function call interrupts"' >
> > events/ipi/ipi_raise/filter  
> 
> The '=' checks if the target_cpus bitmap *only* contains CPU 11. If the cpumask
> contains other CPUs, the filter will skip the call.
> 
> I believe you can use '&' to check whether a cpumask contains a CPU, e.g.
> 
> 	'target_cpus & 11'

11 == 0xb = b1011

So the above would only be true for CPUs 0,1 and 3 ;-)

I think you meant: 'target_cpus & 0x800' 

I tried "1 << 11' but it appears to not allow shifts. I wonder if we should add that?

-- Steve