FAILED: Patch "arm64: Disable branch profiling for all arm64 code" failed to apply to 6.12-stable tree

FAILED: Patch "arm64: Disable branch profiling for all arm64 code" failed to apply to 6.12-stable tree

[Sasha Levin]

The patch below does not apply to the 6.12-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

Thanks,
Sasha

------------------ original commit in Linus's tree ------------------

From f22c81bebf8bda6e54dc132df0ed54f6bf8756f9 Mon Sep 17 00:00:00 2001
From: Breno Leitao <leitao@debian.org>
Date: Tue, 6 Jan 2026 02:16:35 -0800
Subject: [PATCH] arm64: Disable branch profiling for all arm64 code

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(!?).

Rather than playing whack-a-mole with individual files, disable branch
profiling for the entire arch/arm64 tree, similar to what x86 already
does in arch/x86/Kbuild.

Cc: stable@vger.kernel.org
Signed-off-by: Breno Leitao <leitao@debian.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>
---
 arch/arm64/Kbuild | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/arm64/Kbuild b/arch/arm64/Kbuild
index 5bfbf7d79c99b..d876bc0e54211 100644
--- a/arch/arm64/Kbuild
+++ b/arch/arm64/Kbuild
@@ -1,4 +1,8 @@
 # SPDX-License-Identifier: GPL-2.0-only
+
+# Branch profiling isn't noinstr-safe
+subdir-ccflags-$(CONFIG_TRACE_BRANCH_PROFILING) += -DDISABLE_BRANCH_PROFILING
+
 obj-y			+= kernel/ mm/ net/
 obj-$(CONFIG_KVM)	+= kvm/
 obj-$(CONFIG_XEN)	+= xen/
-- 
2.51.0