[PATCH v2 01/10] riscv: Allow to dynamically define VA_BITS

Alexandre Ghiti
2021-09-29T14:52:39Z

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 <alexandre.ghiti@canonical.com>
---
arch/riscv/Kconfig | 10 ----------
arch/riscv/include/asm/pgtable.h | 10 ++++++++--
arch/riscv/include/asm/sparsemem.h | 6 +++++-
3 files changed, 13 insertions(+), 13 deletions(-)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index c1abbc876e5b..ee61ecae3ae0 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -145,16 +145,6 @@ config MMU
Select if you want MMU-based virtualised addressing space
support by paged memory management. If unsure, say 'Y'.

-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_1GB
diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
index 39b550310ec6..e3e03226a50a 100644
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -48,8 +48,14 @@
* 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)
@@ -651,7 +657,7 @@ static inline pmd_t pmdp_establish(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 */

--
2.30.2