Bug 203161

Hello,

a kernel configuration for ppc64 started failing to build between v5.1-rc1 and v5.1-rc2. Bisect led to

commit 8bc086899816214fbc6047c9c7e15fcab49552bf
Author: Ben Hutchings <ben@decadent.org.uk>
Date:   Sun Mar 17 01:17:56 2019 +0000

    powerpc/mm: Only define MAX_PHYSMEM_BITS in SPARSEMEM configurations


Syptoms: *Many* warnings like

In file included from ./arch/powerpc/include/asm/book3s/64/mmu.h:39,
                 from ./arch/powerpc/include/asm/mmu.h:360,
                 from ./arch/powerpc/include/asm/lppaca.h:36,
                 from ./arch/powerpc/include/asm/paca.h:21,
                 from ./arch/powerpc/include/asm/current.h:16,
                 from ./include/linux/thread_info.h:21,
                 from ./include/asm-generic/preempt.h:5,
                 from ./arch/powerpc/include/generated/asm/preempt.h:1,
                 from ./include/linux/preempt.h:78,
                 from ./include/linux/spinlock.h:51,
                 from ./include/linux/seqlock.h:36,
                 from ./include/linux/time.h:6,
                 from ./include/linux/compat.h:10,
                 from arch/powerpc/kernel/asm-offsets.c:18:
./arch/powerpc/include/asm/book3s/64/mmu-hash.h:584:6: warning: "MAX_PHYSMEM_BITS" is not defined, evaluates to 0 [-Wundef]
 #if (MAX_PHYSMEM_BITS > MAX_EA_BITS_PER_CONTEXT)
      ^~~~~~~~~~~~~~~~

... and eventually abort with:

arch/powerpc/mm/slb.c: In function 'slb_allocate_kernel':
arch/powerpc/mm/slb.c:697:37: error: 'MAX_PHYSMEM_BITS' undeclared (first use in this function); did you mean 'SWP_TYPE_BITS'?
   if ((ea & ~REGION_MASK) > (1UL << MAX_PHYSMEM_BITS))
                                     ^~~~~~~~~~~~~~~~
                                     SWP_TYPE_BITS

A ppc64 configuration is attached.

FWIW, built was made using the cross compiler as provided in Debian buster. I can repeat this on native hardware upon request although I strongly doubt this makes any differences. Build command line was

make ARCH=powerpc CROSS_COMPILE=powerpc64-linux-gnu- LDFLAGS= KCPPFLAGS=-fno-pic