linux-kernel - Re: [PATCH 6.6.y 0/4] perf/x86/amd: add LBR capture support outside of hardware events

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Message-ID: <2026010809-matchless-reporter-3129@gregkh>
Date: Thu, 8 Jan 2026 12:11:32 +0100
From: Greg KH <gregkh@...uxfoundation.org>
To: Leon Hwang <leon.hwang@...ux.dev>
Cc: stable@...r.kernel.org, Andrii Nakryiko <andrii@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Jiri Olsa <jolsa@...nel.org>, Namhyung Kim <namhyung@...nel.org>,
	Ian Rogers <irogers@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
	"H . Peter Anvin" <hpa@...or.com>, linux-perf-users@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 6.6.y 0/4] perf/x86/amd: add LBR capture support outside
 of hardware events

On Fri, Jan 02, 2026 at 05:03:16PM +0800, Leon Hwang wrote:
> Hi all,
> 
> This backport wires up AMD perfmon v2 so BPF and other software clients
> can snapshot LBR stacks on demand, similar to the Intel support
> upstream. The series keeps the LBR-freeze path branchless, adds the
> perf_snapshot_branch_stack callback for AMD, and drops the
> sampling-only restriction now that snapshots can be taken from software
> contexts.
> 
> Leon Hwang (4):
>   perf/x86/amd: Ensure amd_pmu_core_disable_all() is always inlined
>   perf/x86/amd: Avoid taking branches before disabling LBR
>   perf/x86/amd: Support capturing LBR from software events
>   perf/x86/amd: Don't reject non-sampling events with configured LBR


Why is this for a stable kernel?  Isn't it a new feature?  If you need
this feature, why not use a newer kernel tree?

thanks,

greg k-h