On Tue, Nov 13, 2018 at 04:29:06PM +0100, Alexander Graf wrote:

I've already stumbled over 2 cases where people got confused about how to
disable kpti on AArch64. In both cases, they used existing x86_64 options
and just applied that to an AArch64 system, expecting it to work.

I think it makes a lot of sense to have compatible kernel command line
parameters whenever we can have them be compatible.

So this patch adds the pti= and no_pti kernel command line options, mapping
them into the existing kpti= command line framework. It preserves the old
syntax to maintain compatibility with older command lines.

While at it, the patch also marks the respective options as dual-arch.

Reported-by: Richard Brown <redacted>
Signed-off-by: Alexander Graf <redacted>

---

v1 -> v2:

  - Actually make it compile. Sorry for the sloppy v1.
---
 Documentation/admin-guide/kernel-parameters.txt |  6 +++---
 arch/arm64/kernel/cpufeature.c                  | 20 +++++++++++++++++++-
 2 files changed, 22 insertions(+), 4 deletions(-)

This patch doesn't help though, right, because kpti= has already been
included with backports etc so the ship has sailed? Yeah, it's not ideal,
but we went over this before:

http://lists.infradead.org/pipermail/linux-arm-kernel/2018-August/598395.html

The thing we really need is the sysfs interface hooking up so you can easily
check the state of the mitigation. Still waiting for a follow-up on that ;)

http://lists.infradead.org/pipermail/linux-arm-kernel/2018-September/603412.html

Will