Re: [PATCH -next] powerpc/book3s64: fix link error with CONFIG_PPC_RADIX_MMU=n

[Christophe Leroy]

Le 05/09/2020 à 13:25, Yang Yingliang a écrit :
Fix link error when CONFIG_PPC_RADIX_MMU is disabled:
powerpc64-linux-gnu-ld: arch/powerpc/platforms/pseries/lpar.o:(.toc+0x0): 
undefined reference to `mmu_pid_bits'

Reported-by: Hulk Robot <hul...@huawei.com>
Signed-off-by: Yang Yingliang <yangyingli...@huawei.com>
---
  arch/powerpc/mm/book3s64/mmu_context.c | 4 ++++

In your commit log, you are just mentionning 
arch/powerpc/platforms/pseries/lpar.o, which is right.

You shouldn't need to modify arch/powerpc/mm/book3s64/mmu_context.c at 
all, see below.

  arch/powerpc/platforms/pseries/lpar.c  | 2 ++
  2 files changed, 6 insertions(+)

diff --git a/arch/powerpc/mm/book3s64/mmu_context.c 
b/arch/powerpc/mm/book3s64/mmu_context.c
index 0ba30b8b935b..a8e292cd88f0 100644
--- a/arch/powerpc/mm/book3s64/mmu_context.c
+++ b/arch/powerpc/mm/book3s64/mmu_context.c
@@ -152,6 +152,7 @@ void hash__setup_new_exec(void)
  
  static int radix__init_new_context(struct mm_struct *mm)
  {
+#ifdef CONFIG_PPC_RADIX_MMU

This shouldn't be required. radix__init_new_context() is only called 
when radix_enabled() returns true.
As it is a static function, when it is not called it gets optimised 
away, so you will never get an undefined reference to `mmu_pid_bits` there.

        unsigned long rts_field;
        int index, max_id;
  
@@ -177,6 +178,9 @@ static int radix__init_new_context(struct mm_struct *mm)
        mm->context.hash_context = NULL;
  
  	return index;
+#else
+       return -ENOTSUPP;
+#endif
  }
  
  int init_new_context(struct task_struct *tsk, struct mm_struct *mm)
diff --git a/arch/powerpc/platforms/pseries/lpar.c 
b/arch/powerpc/platforms/pseries/lpar.c
index baf24eacd268..e454e218dbba 100644
--- a/arch/powerpc/platforms/pseries/lpar.c
+++ b/arch/powerpc/platforms/pseries/lpar.c
@@ -1726,10 +1726,12 @@ void __init hpte_init_pseries(void)
  
  void radix_init_pseries(void)
  {
+#ifdef CONFIG_PPC_RADIX_MMU

This function is only called from 
/arch/powerpc/mm/book3s64/radix_pgtable.c which is only built when 
CONFIG_PPC_RADIX_MMU is selected.

So the entire function should be encloded in the #ifdef.

        pr_info("Using radix MMU under hypervisor\n");
  
  	pseries_lpar_register_process_table(__pa(process_tb),
                                                0, PRTB_SIZE_SHIFT - 12);
+#endif
  }
  
  #ifdef CONFIG_PPC_SMLPAR


Christophe