Re: [PATCH 0/4] ARM: Support KFENCE feature

[Marco Elver]

On Wed, Aug 25, 2021 at 12:14PM +0200, Marco Elver wrote:
> On Wed, 25 Aug 2021 at 11:17, Kefeng Wang <wangkefeng.wang@xxxxxxxxxx> wrote:
> > The patch 1~3 is to support KFENCE feature on ARM.
> >
> > NOTE:
> > The context of patch2/3 changes in arch/arm/mm/fault.c is based on link[1],
> > which make some refactor and cleanup about page fault.
> >
> > kfence_test is not useful when kfence is not enabled, skip kfence test
> > when kfence not enabled in patch4.
> >
> > I tested the kfence_test on ARM QEMU with or without ARM_LPAE and all passed.
> 
> Thank you for enabling KFENCE on ARM -- I'll leave arch-code review to
> an ARM maintainer.
> 
> However, as said on the patch, please drop the change to the
> kfence_test and associated changes. This is working as intended; while
> you claim that it takes a long time to run when disabled, when running
> manually you just should not run it when disabled. There are CI
> systems that rely on the KUnit test output and the fact that the
> various test cases say "not ok" etc. Changing that would mean such CI
> systems would no longer fail if KFENCE was accidentally disabled (once
> KFENCE is enabled on various CI, which we'd like to do at some point).
> There are ways to fail the test faster, but they all complicate the
> test for no good reason. (And the addition of a new exported function
> that is essentially useless.)

I spoke too soon -- we export __kfence_pool, and that's good enough to
fail the test fast if KFENCE was disabled at boot:

	https://lkml.kernel.org/r/20210825105533.1247922-1-elver@xxxxxxxxxx

will do the trick. So please drop your patch 4/4 here.

Thanks,
-- Marco