Re: microwatt_defconfig broken: fined reference to `hash__tlb_flush'

[Christophe Leroy <christophe.leroy@csgroup.eu>]

Le 17/02/2023 à 18:14, Jan-Benedict Glaw a écrit :
> 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


The fix is available here : 
https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git/commit/?id=4302abc628fc0dc08e5855f21bbfaed407a72bc3


> 
> 
> 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@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@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