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From: Sasha Levin <sashal@kernel.org>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: Samuel Holland <samuel.holland@sifive.com>,
	Jesse Taube <mr.bossman075@gmail.com>,
	Palmer Dabbelt <palmer@rivosinc.com>,
	Sasha Levin <sashal@kernel.org>,
	paul.walmsley@sifive.com, palmer@dabbelt.com,
	aou@eecs.berkeley.edu, alexghiti@rivosinc.com,
	namcao@linutronix.de, bjorn@rivosinc.com,
	vincenzo.frascino@arm.com, stuart.menefy@codasip.com,
	luxu.kernel@bytedance.com, david@redhat.com,
	akpm@linux-foundation.org, libang.li@antgroup.com,
	abrestic@rivosinc.com, anshuman.khandual@arm.com,
	yongxuan.wang@sifive.com, linux-riscv@lists.infradead.org
Subject: [PATCH AUTOSEL 6.6 016/294] riscv: Allow NOMMU kernels to access all of RAM
Date: Mon,  5 May 2025 18:51:56 -0400	[thread overview]
Message-ID: <20250505225634.2688578-16-sashal@kernel.org> (raw)
In-Reply-To: <20250505225634.2688578-1-sashal@kernel.org>

From: Samuel Holland <samuel.holland@sifive.com>

[ Upstream commit 2c0391b29b27f315c1b4c29ffde66f50b29fab99 ]

NOMMU kernels currently cannot access memory below the kernel link
address. Remove this restriction by setting PAGE_OFFSET to the actual
start of RAM, as determined from the devicetree. The kernel link address
must be a constant, so keep using CONFIG_PAGE_OFFSET for that purpose.

Signed-off-by: Samuel Holland <samuel.holland@sifive.com>
Reviewed-by: Jesse Taube <mr.bossman075@gmail.com>
Link: https://lore.kernel.org/r/20241026171441.3047904-3-samuel.holland@sifive.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 arch/riscv/include/asm/page.h    | 12 ++++--------
 arch/riscv/include/asm/pgtable.h |  2 +-
 2 files changed, 5 insertions(+), 9 deletions(-)

diff --git a/arch/riscv/include/asm/page.h b/arch/riscv/include/asm/page.h
index 4d1f58848129e..dbb9d0d0f405e 100644
--- a/arch/riscv/include/asm/page.h
+++ b/arch/riscv/include/asm/page.h
@@ -26,12 +26,9 @@
  * When not using MMU this corresponds to the first free page in
  * physical memory (aligned on a page boundary).
  */
-#ifdef CONFIG_64BIT
 #ifdef CONFIG_MMU
+#ifdef CONFIG_64BIT
 #define PAGE_OFFSET		kernel_map.page_offset
-#else
-#define PAGE_OFFSET		_AC(CONFIG_PAGE_OFFSET, UL)
-#endif
 /*
  * By default, CONFIG_PAGE_OFFSET value corresponds to SV57 address space so
  * define the PAGE_OFFSET value for SV48 and SV39.
@@ -41,6 +38,9 @@
 #else
 #define PAGE_OFFSET		_AC(CONFIG_PAGE_OFFSET, UL)
 #endif /* CONFIG_64BIT */
+#else
+#define PAGE_OFFSET		((unsigned long)phys_ram_base)
+#endif /* CONFIG_MMU */
 
 #ifndef __ASSEMBLY__
 
@@ -97,11 +97,7 @@ typedef struct page *pgtable_t;
 #define MIN_MEMBLOCK_ADDR      0
 #endif
 
-#ifdef CONFIG_MMU
 #define ARCH_PFN_OFFSET		(PFN_DOWN((unsigned long)phys_ram_base))
-#else
-#define ARCH_PFN_OFFSET		(PAGE_OFFSET >> PAGE_SHIFT)
-#endif /* CONFIG_MMU */
 
 struct kernel_mapping {
 	unsigned long page_offset;
diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
index f540b2625714d..332a6bf72b1d5 100644
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -12,7 +12,7 @@
 #include <asm/pgtable-bits.h>
 
 #ifndef CONFIG_MMU
-#define KERNEL_LINK_ADDR	PAGE_OFFSET
+#define KERNEL_LINK_ADDR	_AC(CONFIG_PAGE_OFFSET, UL)
 #define KERN_VIRT_SIZE		(UL(-1))
 #else
 
-- 
2.39.5


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           reply	other threads:[~2025-05-06  2:24 UTC|newest]

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