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From:   Arnd Bergmann <arnd@arndb.de>
Date:   Tue, 11 Jan 2022 17:23:14 +0100
Message-ID: <CAK8P3a3SpYe101RSFD5rzbTQNyQyfG1eb1sCY+rBO-DKVqBdBw@mail.gmail.com>
Subject: Re: [ANNOUNCE] "Fast Kernel Headers" Tree -v2
To:     Arnd Bergmann <arnd@arndb.de>
Cc:     Ingo Molnar <mingo@kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-arch <linux-arch@vger.kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Nathan Chancellor <nathan@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Ard Biesheuvel <ardb@kernel.org>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        Jonathan Corbet <corbet@lwn.net>
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On Mon, Jan 10, 2022 at 11:03 PM Arnd Bergmann <arnd@arndb.de> wrote:
> On Sat, Jan 8, 2022 at 5:26 PM Ingo Molnar <mingo@kernel.org> wrote:
> I've started building randconfig kernels for arm64 and x86, and fixing
> up things that come up, a few things I have noticed out so far:

I have run into a couple more specific issues:

* net/smc/smc_ib.c:824:26: error: implicit declaration of function
'cache_line_size' [-Werror=implicit-function-declaration]
cache_line_size is generally provided by linux/cache.h, which includes
asm/cache.h.
This works on arm64, but not on x86, where asm/cache.h would have to include
asm/cpufeature.h, and but it would be good to avoid that because of the implicit
linux/percpu.h and linux/bitops.h inclusions. Also, if I add the
include, I get this
build failure instead: include/linux/smp_types.h:88:33: error:
requested alignment '20'
is not a positive power of 2

* arm64 has a couple of issues around asm/memory.h, linux/mm_types.h
and asm/page.h
that can cause loops. I think my latest version has it figured out,
but there is probably
room for optimization.

* There is no general way to get the get_order() definition, other
than including
asm/page.h from .c files. On arm64, this shows up in a couple of files after the
cleanup. Only xtensa and ia64 define their own version of get_order(),
and I think
we should just remove those and move the generic version to linux/getorder.h,
where any file using it can pick it up. For randconfig builds, I had
to add asm/page.h
to net/xdp/xsk_queue.c, mm/memtest.c and
drivers/target/iscsi/iscsi_target_nego.c,
after I removed the indirect include from arch/arm64/include/asm/mmu.h
in the previous step.

         Arnd