Re: [RFC PATCH 04/12] riscv: Allow to dynamically define VA_BITS

[Alex Ghiti]

Le 1/5/21 à 7:06 AM, Anup Patel a écrit :

On Tue, Jan 5, 2021 at 1:33 AM Alexandre Ghiti <a...@ghiti.fr> wrote:

With 4-level page table folding at runtime, we don't know at compile time
the size of the virtual address space so we must set VA_BITS dynamically
so that sparsemem reserves the right amount of memory for struct pages.

Signed-off-by: Alexandre Ghiti <a...@ghiti.fr>
---
  arch/riscv/Kconfig                 | 10 ----------
  arch/riscv/include/asm/pgtable.h   | 11 +++++++++--
  arch/riscv/include/asm/sparsemem.h |  6 +++++-
  3 files changed, 14 insertions(+), 13 deletions(-)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 44377fd7860e..2979a44103be 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -122,16 +122,6 @@ config ZONE_DMA32
         bool
         default y if 64BIT

-config VA_BITS
-       int
-       default 32 if 32BIT
-       default 39 if 64BIT
-
-config PA_BITS
-       int
-       default 34 if 32BIT
-       default 56 if 64BIT
-
  config PAGE_OFFSET
         hex
         default 0xC0000000 if 32BIT && MAXPHYSMEM_2GB
diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
index 102b728ca146..c7973bfd65bc 100644
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -43,8 +43,14 @@
   * struct pages to map half the virtual address space. Then
   * position vmemmap directly below the VMALLOC region.
   */
+#ifdef CONFIG_64BIT
+#define VA_BITS                39
+#else
+#define VA_BITS                32
+#endif
+
  #define VMEMMAP_SHIFT \
-       (CONFIG_VA_BITS - PAGE_SHIFT - 1 + STRUCT_PAGE_MAX_SHIFT)
+       (VA_BITS - PAGE_SHIFT - 1 + STRUCT_PAGE_MAX_SHIFT)
  #define VMEMMAP_SIZE   BIT(VMEMMAP_SHIFT)
  #define VMEMMAP_END    (VMALLOC_START - 1)
  #define VMEMMAP_START  (VMALLOC_START - VMEMMAP_SIZE)
@@ -83,6 +89,7 @@
  #endif /* CONFIG_64BIT */

  #ifdef CONFIG_MMU
+
  /* Number of entries in the page global directory */
  #define PTRS_PER_PGD    (PAGE_SIZE / sizeof(pgd_t))
  /* Number of entries in the page table */
@@ -453,7 +460,7 @@ static inline int ptep_clear_flush_young(struct 
vm_area_struct *vma,
   * and give the kernel the other (upper) half.
   */
  #ifdef CONFIG_64BIT
-#define KERN_VIRT_START        (-(BIT(CONFIG_VA_BITS)) + TASK_SIZE)
+#define KERN_VIRT_START        (-(BIT(VA_BITS)) + TASK_SIZE)
  #else
  #define KERN_VIRT_START        FIXADDR_START
  #endif
diff --git a/arch/riscv/include/asm/sparsemem.h 
b/arch/riscv/include/asm/sparsemem.h
index 45a7018a8118..63acaecc3374 100644
--- a/arch/riscv/include/asm/sparsemem.h
+++ b/arch/riscv/include/asm/sparsemem.h
@@ -4,7 +4,11 @@
  #define _ASM_RISCV_SPARSEMEM_H

  #ifdef CONFIG_SPARSEMEM
-#define MAX_PHYSMEM_BITS       CONFIG_PA_BITS
+#ifdef CONFIG_64BIT
+#define MAX_PHYSMEM_BITS       56
+#else
+#define MAX_PHYSMEM_BITS       34
+#endif /* CONFIG_64BIT */
  #define SECTION_SIZE_BITS      27
  #endif /* CONFIG_SPARSEMEM */

--
2.20.1

Looks good to me.

Reviewed-by: Anup Patel <a...@brainfault.org>

Thanks,

Regards,
Anup

Alex