On Tue, Jan 06, 2026 at 02:16:35AM -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(!?).
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 Fixes: ec6d06efb0bac ("arm64: Add support for CONFIG_DEBUG_VIRTUAL") Signed-off-by: Breno Leitao leitao@debian.org
I don't think ec6d06efb0bac is to blame here, and CONFIG_DEBUG_VIRTUAL is unsound in a number of places, so I'd prefer to remove that Fixes tag and backport this for all stable trees.
Regardless, I'm in favour of disabling CONFIG_DEBUG_VIRTUAL widely, so:
Acked-by: Mark Rutland mark.rutland@arm.com
Mark.
Changes in v2:
- Expand the scope to arch/arm64 instead of just physaddr.c
- Link to v1: https://lore.kernel.org/all/20251231-annotated-v1-1-9db1c0d03062@debian.org/
arch/arm64/Kbuild | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/arch/arm64/Kbuild b/arch/arm64/Kbuild index 5bfbf7d79c99..d876bc0e5421 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/
base-commit: c8ebd433459bcbf068682b09544e830acd7ed222 change-id: 20251231-annotated-75de3f33cd7b
Best regards,
Breno Leitao leitao@debian.org