linux-kernel - [RFC PATCH 2/7] riscv: Allow to dynamically define VA

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Date:   Sun, 22 Mar 2020 07:00:23 -0400
From:   Alexandre Ghiti <alex@...ti.fr>
To:     Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Zong Li <zong.li@...ive.com>, Anup Patel <anup@...infault.org>,
        Christoph Hellwig <hch@....de>,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc:     Alexandre Ghiti <alex@...ti.fr>
Subject: [RFC PATCH 2/7] riscv: Allow to dynamically define VA_BITS

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 <alex@...ti.fr>
---
 arch/riscv/Kconfig                 | 10 ----------
 arch/riscv/include/asm/pgtable.h   | 10 +++++++++-
 arch/riscv/include/asm/sparsemem.h |  2 +-
 3 files changed, 10 insertions(+), 12 deletions(-)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index f5f3d474504d..8e4b1cbcf2c2 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -99,16 +99,6 @@ 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 185ffe3723ec..dce401eed1d3 100644
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -26,6 +26,14 @@
 #endif /* CONFIG_64BIT */
 
 #ifdef CONFIG_MMU
+#ifdef CONFIG_64BIT
+#define VA_BITS		39
+#define PA_BITS		56
+#else
+#define VA_BITS		32
+#define PA_BITS		34
+#endif
+
 /* Number of entries in the page global directory */
 #define PTRS_PER_PGD    (PAGE_SIZE / sizeof(pgd_t))
 /* Number of entries in the page table */
@@ -108,7 +116,7 @@ extern pgd_t swapper_pg_dir[];
  * position vmemmap directly below the VMALLOC region.
  */
 #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)
diff --git a/arch/riscv/include/asm/sparsemem.h b/arch/riscv/include/asm/sparsemem.h
index 45a7018a8118..f08d72155bc8 100644
--- a/arch/riscv/include/asm/sparsemem.h
+++ b/arch/riscv/include/asm/sparsemem.h
@@ -4,7 +4,7 @@
 #define _ASM_RISCV_SPARSEMEM_H
 
 #ifdef CONFIG_SPARSEMEM
-#define MAX_PHYSMEM_BITS	CONFIG_PA_BITS
+#define MAX_PHYSMEM_BITS	PA_BITS
 #define SECTION_SIZE_BITS	27
 #endif /* CONFIG_SPARSEMEM */
 
-- 
2.20.1