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

On 2020/9/6 14:50, Christophe Leroy wrote:

Le 05/09/2020 à 13:25, Yang Yingliang a écrit :

quoted

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 <redacted>
Signed-off-by: Yang Yingliang <redacted>
---
  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.

quoted

  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.

powerpc64-linux-gnu-ld: 
arch/powerpc/mm/book3s64/mmu_context.o:(.toc+0x0): undefined reference 
to `mmu_pid_bits'
powerpc64-linux-gnu-ld: 
arch/powerpc/mm/book3s64/mmu_context.o:(.toc+0x8): undefined reference 
to `mmu_base_pid'


mmu_context.c is always compiled, it uses mmu_pid_bits and mmu_base_pid.

quoted

      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.

OK, I will send a v2 later.

quoted

      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
.