microwatt_defconfig broken: fined reference to `hash__tlb_flush'

[Jan-Benedict Glaw]

Hi!

My CI builds showed that the microwatt_defconfig broke somewhere between
(upstream Linus) 6d796c50f84ca79f1722bb131799e5a5710c4700 (last known good, log
at [1]) and 033c40a89f55525139fd5b6342281b09b97d05bf (first known bad, log at
[2]) with this:

[...]
make V=1 ARCH=powerpc CROSS_COMPILE=powerpc64le-linux- INSTALL_MOD_PATH=/var/lib/laminar/run/linux-powerpc-microwatt_defconfig/28/linux-powerpc-microwatt_defconfig INSTALL_DTBS_PATH=/var/lib/laminar/run/linux-powerpc-microwatt_defconfig/28/linux-powerpc-microwatt_defconfig all
[...]
[mk all 2023-02-17 01:42:27] + powerpc64le-linux-ld -EL -z noexecstack --no-warn-rwx-segments -Bstatic --build-id=sha1 --orphan-handling=warn --script=./arch/powerpc/kernel/vmlinux.lds --strip-debug -o .tmp_vmlinux.kallsyms1 --whole-archive vmlinux.a init/version-timestamp.o --no-whole-archive --start-group lib/lib.a --end-group
[mk all 2023-02-17 01:42:28] powerpc64le-linux-ld: mm/memory.o: in function `tlb_flush_mmu_tlbonly':
[mk all 2023-02-17 01:42:28] memory.c:(.text+0x320): undefined reference to `hash__tlb_flush'
[mk all 2023-02-17 01:42:28] powerpc64le-linux-ld: mm/mmu_gather.o: in function `tlb_flush_mmu_tlbonly':
[mk all 2023-02-17 01:42:28] mmu_gather.c:(.text+0xe0): undefined reference to `hash__tlb_flush'
[mk all 2023-02-17 01:42:28] powerpc64le-linux-ld: mm/mprotect.o: in function `change_protection':
[mk all 2023-02-17 01:42:28] mprotect.c:(.text+0x59c): undefined reference to `hash__tlb_flush'
[mk all 2023-02-17 01:42:28] powerpc64le-linux-ld: mm/madvise.o: in function `tlb_end_vma.isra.0':
[mk all 2023-02-17 01:42:28] madvise.c:(.text+0x1f0): undefined reference to `hash__tlb_flush'
[mk all 2023-02-17 01:42:28] make[1]: *** [scripts/Makefile.vmlinux:35: vmlinux] Error 1
[mk all 2023-02-17 01:42:28] make: *** [Makefile:1264: vmlinux] Error 2


It's not yet bisected fully, but I guess it was caused while trying to
fix a missing tlb flush:

commit 1665c027afb225882a5a0b014c45e84290b826c2
Author: Michael Ellerman <mpe at ellerman.id.au>
Date:   Tue Jan 31 22:14:07 2023 +1100

    powerpc/64s: Reconnect tlb_flush() to hash__tlb_flush()
    
    Commit baf1ed24b27d ("powerpc/mm: Remove empty hash__ functions")
    removed some empty hash MMU flushing routines, but got a bit overeager
    and also removed the call to hash__tlb_flush() from tlb_flush().
    
    In regular use this doesn't lead to any noticable breakage, which is a
    little concerning. Presumably there are flushes happening via other
    paths such as arch_leave_lazy_mmu_mode(), and/or a bit of luck.
    
    Fix it by reinstating the call to hash__tlb_flush().
    
    Fixes: baf1ed24b27d ("powerpc/mm: Remove empty hash__ functions")
    Signed-off-by: Michael Ellerman <mpe at ellerman.id.au>
    Link: https://lore.kernel.org/r/20230131111407.806770-1-mpe@ellerman.id.au

MfG, JBG


[1] http://toolchain.lug-owl.de/laminar/jobs/linux-powerpc-microwatt_defconfig/27
[2] http://toolchain.lug-owl.de/laminar/jobs/linux-powerpc-microwatt_defconfig/28
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