From: Will Deacon <will@kernel.org>
To: Breno Leitao <leitao@debian.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
Mark Rutland <mark.rutland@arm.com>,
Laura Abbott <labbott@redhat.com>,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org,
Steven Rostedt <rostedt@goodmis.org>,
Masami Hiramatsu <mhiramat@kernel.org>,
puranjay@kernel.org, usamaarif642@gmail.com,
kernel-team@meta.com, stable@vger.kernel.org
Subject: Re: [PATCH] arm64/mm: Fix annotated branch unbootable kernel
Date: Mon, 5 Jan 2026 21:15:40 +0000 [thread overview]
Message-ID: <aVwp_BJx84gXHPlD@willie-the-truck> (raw)
In-Reply-To: <20251231-annotated-v1-1-9db1c0d03062@debian.org>
On Wed, Dec 31, 2025 at 04:44:05AM -0800, Breno Leitao wrote:
> The arm64 kernel doesn't boot with annotated branches
> (PROFILE_ANNOTATED_BRANCHES) enabled and CONFIG_DEBUG_VIRTUAL together.
>
> Bisecting it, I found that disabling branch profiling in arch/arm64/mm
> solved the problem. Narrowing down a bit further, I found that
> physaddr.c is the file that needs to have branch profiling disabled to
> get the machine to boot.
>
> I suspect that it might invoke some ftrace helper very early in the boot
> process and ftrace is still not enabled(!?).
>
> Disable branch profiling for physaddr.o to allow booting an arm64
> machine with CONFIG_PROFILE_ANNOTATED_BRANCHES and
> CONFIG_DEBUG_VIRTUAL together.
>
> Cc: stable@vger.kernel.org
> Fixes: ec6d06efb0bac ("arm64: Add support for CONFIG_DEBUG_VIRTUAL")
> Signed-off-by: Breno Leitao <leitao@debian.org>
> ---
> Another approach is to disable profiling on all arch/arm64 code, similarly to
> x86, where DISABLE_BRANCH_PROFILING is called for all arch/x86 code. See
> commit 2cbb20b008dba ("tracing: Disable branch profiling in noinstr
> code").
Yes, let's start with arch/arm64/. We know that's safe and then if
somebody wants to make it finer-grained, it's on them to figure out a
way to do it without playing whack-a-mole.
Will
next prev parent reply other threads:[~2026-01-05 21:15 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-12-31 12:44 [PATCH] arm64/mm: Fix annotated branch unbootable kernel Breno Leitao
2026-01-05 21:15 ` Will Deacon [this message]
2026-01-09 19:47 ` Steven Rostedt
2026-01-09 19:50 ` Steven Rostedt
2026-01-12 9:42 ` Breno Leitao
2026-01-12 15:46 ` Steven Rostedt
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