Re: [PATCH v6 15/18] powerpc/64s: Always define arch unmapped area calls

Excerpts from Nicholas Piggin's message of December 9, 2021 6:25 pm:

Excerpts from Christophe Leroy's message of December 8, 2021 7:38 pm:

quoted

Le 01/12/2021 à 15:41, Nicholas Piggin a écrit :

quoted

To avoid any functional changes to radix paths when building with hash
MMU support disabled (and CONFIG_PPC_MM_SLICES=n), always define the
arch get_unmapped_area calls on 64s platforms.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
  arch/powerpc/include/asm/book3s/64/hash.h |  4 ---
  arch/powerpc/include/asm/book3s/64/mmu.h  |  6 ++++
  arch/powerpc/mm/hugetlbpage.c             | 16 ++++++---
  arch/powerpc/mm/mmap.c                    | 40 +++++++++++++++++++----
  arch/powerpc/mm/slice.c                   | 20 ------------
  5 files changed, 51 insertions(+), 35 deletions(-)

diff --git a/arch/powerpc/include/asm/book3s/64/hash.h b/arch/powerpc/include/asm/book3s/64/hash.h
index 674fe0e890dc..a7a0572f3846 100644
--- a/arch/powerpc/include/asm/book3s/64/hash.h
+++ b/arch/powerpc/include/asm/book3s/64/hash.h

@@ -99,10 +99,6 @@
   * Defines the address of the vmemap area, in its own region on
   * hash table CPUs.
   */
-#ifdef CONFIG_PPC_MM_SLICES
-#define HAVE_ARCH_UNMAPPED_AREA
-#define HAVE_ARCH_UNMAPPED_AREA_TOPDOWN
-#endif /* CONFIG_PPC_MM_SLICES */
  
  /* PTEIDX nibble */
  #define _PTEIDX_SECONDARY	0x8

diff --git a/arch/powerpc/include/asm/book3s/64/mmu.h b/arch/powerpc/include/asm/book3s/64/mmu.h
index c02f42d1031e..015d7d972d16 100644
--- a/arch/powerpc/include/asm/book3s/64/mmu.h
+++ b/arch/powerpc/include/asm/book3s/64/mmu.h

@@ -4,6 +4,12 @@
  
  #include <asm/page.h>
  
+#ifdef CONFIG_HUGETLB_PAGE
+#define HAVE_ARCH_HUGETLB_UNMAPPED_AREA
+#endif
+#define HAVE_ARCH_UNMAPPED_AREA
+#define HAVE_ARCH_UNMAPPED_AREA_TOPDOWN
+
  #ifndef __ASSEMBLY__
  /*
   * Page size definition

diff --git a/arch/powerpc/mm/hugetlbpage.c b/arch/powerpc/mm/hugetlbpage.c
index 82d8b368ca6d..ddead41e2194 100644
--- a/arch/powerpc/mm/hugetlbpage.c
+++ b/arch/powerpc/mm/hugetlbpage.c

@@ -542,20 +542,26 @@ struct page *follow_huge_pd(struct vm_area_struct *vma,
  	return page;
  }
  
-#ifdef CONFIG_PPC_MM_SLICES
+#ifdef HAVE_ARCH_HUGETLB_UNMAPPED_AREA
+static inline int file_to_psize(struct file *file)
+{
+	struct hstate *hstate = hstate_file(file);
+	return shift_to_mmu_psize(huge_page_shift(hstate));
+}
+
  unsigned long hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
  					unsigned long len, unsigned long pgoff,
  					unsigned long flags)
  {
-	struct hstate *hstate = hstate_file(file);
-	int mmu_psize = shift_to_mmu_psize(huge_page_shift(hstate));
-
  #ifdef CONFIG_PPC_RADIX_MMU
  	if (radix_enabled())
  		return radix__hugetlb_get_unmapped_area(file, addr, len,
  						       pgoff, flags);
  #endif
-	return slice_get_unmapped_area(addr, len, flags, mmu_psize, 1);
+#ifdef CONFIG_PPC_MM_SLICES
+	return slice_get_unmapped_area(addr, len, flags, file_to_psize(file), 1);
+#endif
+	BUG();

We shouldn't had new instances of BUG().

BUILD_BUG() should do the trick here.

quoted

  }
  #endif
  

diff --git a/arch/powerpc/mm/mmap.c b/arch/powerpc/mm/mmap.c
index ae683fdc716c..c475cf810aa8 100644
--- a/arch/powerpc/mm/mmap.c
+++ b/arch/powerpc/mm/mmap.c

@@ -80,6 +80,7 @@ static inline unsigned long mmap_base(unsigned long rnd,
  	return PAGE_ALIGN(DEFAULT_MAP_WINDOW - gap - rnd);
  }
  
+#ifdef HAVE_ARCH_UNMAPPED_AREA
  #ifdef CONFIG_PPC_RADIX_MMU
  /*
   * Same function as generic code used only for radix, because we don't need to overload

@@ -181,11 +182,42 @@ radix__arch_get_unmapped_area_topdown(struct file *filp,
  	 */
  	return radix__arch_get_unmapped_area(filp, addr0, len, pgoff, flags);
  }
+#endif
+
+unsigned long arch_get_unmapped_area(struct file *filp,
+				     unsigned long addr,
+				     unsigned long len,
+				     unsigned long pgoff,
+				     unsigned long flags)
+{
+#ifdef CONFIG_PPC_MM_SLICES
+	return slice_get_unmapped_area(addr, len, flags,
+				       mm_ctx_user_psize(&current->mm->context), 0);
+#else
+	BUG();

Same.

And the #else isn't needed

quoted

+#endif
+}
+
+unsigned long arch_get_unmapped_area_topdown(struct file *filp,
+					     const unsigned long addr0,
+					     const unsigned long len,
+					     const unsigned long pgoff,
+					     const unsigned long flags)
+{
+#ifdef CONFIG_PPC_MM_SLICES
+	return slice_get_unmapped_area(addr0, len, flags,
+				       mm_ctx_user_psize(&current->mm->context), 1);
+#else
+	BUG();

Same

And the #else isn't needed

Fair enough. I'll see if mpe can squash in an incremental patch.

Ah no we can't do that here because arch_get_unmapped_area* is not static
so BUILD_BUG() triggers.

I think we can just look at how it could be improved in future patches.

Thanks,
Nick