linux-kernel - Re: [PATCH v3 2/2] perf bpf-filter: Enable events manually

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Message-ID: <560548ac0ca1f7be7cfb77e34745f86075df2f41.camel@linux.ibm.com>
Date: Wed, 06 Aug 2025 13:29:51 +0200
From: Ilya Leoshkevich <iii@...ux.ibm.com>
To: Thomas Richter <tmricht@...ux.ibm.com>,
        Alexander Gordeev
	 <agordeev@...ux.ibm.com>
Cc: Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann
 <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>, Ian Rogers
 <irogers@...gle.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>, bpf@...r.kernel.org,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-s390@...r.kernel.org, Jiri Olsa	
 <jolsa@...nel.org>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik	
 <gor@...ux.ibm.com>
Subject: Re: [PATCH v3 2/2] perf bpf-filter: Enable events manually

On Wed, 2025-08-06 at 11:29 +0200, Thomas Richter wrote:
> On 8/5/25 16:14, Alexander Gordeev wrote:
> > On Tue, Aug 05, 2025 at 02:54:05PM +0200, Ilya Leoshkevich wrote:
> > 
> > Hi Thomas,
> > 
> > The below comments date to the initial version, so the question is
> > rather to you:
> > 
> > > On linux-next
> > 
> > This line is extra.
> 
> I just wanted to let readers know which repo to look at.
> 
> > 
> > > commit b4c658d4d63d61 ("perf target: Remove uid from target")
> > > introduces a regression on s390. In fact the regression exists
> > > on all platforms when the event supports auxiliary data
> > > gathering.
> > 
> > So which commit it actually fixes: the above, the below or the
> > both?
> > 
> > > Fixes: 63f2f5ee856ba ("libbpf: add ability to attach/detach BPF
> > > program to perf event")
> > 
> > Thanks!
> > 
> 
> Good question!  Pick what you like... :-)
> 
> The issue in question originates from a patch set of 10 patches.
> The patch set rebuilds event sample with filtering and migrates
> from perf tool's selective process picking to more generic eBPF
> filtering using eBPF programs hooked to perf events.
> 
> To be precise, the issue Ilya's  patch fixes is this:
> Fixes: 63f2f5ee856ba ("libbpf: add ability to attach/detach BPF
> program to perf event")
> 
> However the issue (perf failure) does *NOT* show up until this patch
> is applied:
> commit b4c658d4d63d61 ("perf target: Remove uid from target")

I think I will switch the Fixes: tag to b4c658d4d63d61 then, because
IIUC it is one of the factors that drives backporting decisions, and
it does not make too much sense to backport it to earlier kernels.

> There are some patches in between the two (when you look at the
> complete patch set),
> but they do not affect the result.
> 
> Hope that helps.