Unverified Commit 2c0391b2 authored by Samuel Holland's avatar Samuel Holland Committed by Palmer Dabbelt
Browse files

riscv: Allow NOMMU kernels to access all of RAM 



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: default avatarSamuel Holland <samuel.holland@sifive.com>
Reviewed-by: default avatarJesse Taube <mr.bossman075@gmail.com>
Link: https://lore.kernel.org/r/20241026171441.3047904-3-samuel.holland@sifive.com


Signed-off-by: default avatarPalmer Dabbelt <palmer@rivosinc.com>
parent bffada82

arch/riscv/include/asm/page.h

+4 −8
Original line number Diff line number Diff line
@@ -24,12 +24,9 @@ 
 * 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.
@@ -39,6 +36,9 @@ 
#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__
@@ -95,11 +95,7 @@ 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;

arch/riscv/include/asm/pgtable.h

+1 −1
Original line number Diff line number Diff line
@@ -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