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: [email protected] > Fixes: ec6d06efb0bac ("arm64: Add support for CONFIG_DEBUG_VIRTUAL") > Signed-off-by: Breno Leitao <[email protected]>
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 <[email protected]> Mark. > --- > Changes in v2: > - Expand the scope to arch/arm64 instead of just physaddr.c > - Link to v1: > https://lore.kernel.org/all/[email protected]/ > --- > 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 <[email protected]> >
