Unverified Commit ef69d255 authored by Alexandre Ghiti's avatar Alexandre Ghiti Committed by Palmer Dabbelt
Browse files

riscv: Move early dtb mapping into the fixmap region 



riscv establishes 2 virtual mappings:

- early_pg_dir maps the kernel which allows to discover the system
  memory
- swapper_pg_dir installs the final mapping (linear mapping included)

We used to map the dtb in early_pg_dir using DTB_EARLY_BASE_VA, and this
mapping was not carried over in swapper_pg_dir. It happens that
early_init_fdt_scan_reserved_mem() must be called before swapper_pg_dir is
setup otherwise we could allocate reserved memory defined in the dtb.
And this function initializes reserved_mem variable with addresses that
lie in the early_pg_dir dtb mapping: when those addresses are reused
with swapper_pg_dir, this mapping does not exist and then we trap.

The previous "fix" was incorrect as early_init_fdt_scan_reserved_mem()
must be called before swapper_pg_dir is set up otherwise we could
allocate in reserved memory defined in the dtb.

So move the dtb mapping in the fixmap region which is established in
early_pg_dir and handed over to swapper_pg_dir.

Fixes: 922b0375 ("riscv: Fix memblock reservation for device tree blob")
Fixes: 8f3a2b4a ("RISC-V: Move DT mapping outof fixmap")
Fixes: 50e63dd8 ("riscv: fix reserved memory setup")
Reported-by: default avatarConor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/all/f8e67f82-103d-156c-deb0-d6d6e2756f5e@microchip.com/


Signed-off-by: default avatarAlexandre Ghiti <alexghiti@rivosinc.com>
Reviewed-by: default avatarConor Dooley <conor.dooley@microchip.com>
Tested-by: default avatarConor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20230329081932.79831-2-alexghiti@rivosinc.com


Cc: stable@vger.kernel.org
Signed-off-by: default avatarPalmer Dabbelt <palmer@rivosinc.com>
parent 8d736482

Documentation/riscv/vm-layout.rst

+3 −3
Original line number Diff line number Diff line
@@ -47,7 +47,7 @@ RISC-V Linux Kernel SV39 
                                                              | Kernel-space virtual memory, shared between all processes:

  ____________________________________________________________|___________________________________________________________

                    |            |                  |         |

   ffffffc6fee00000 | -228    GB | ffffffc6feffffff |    2 MB | fixmap

   ffffffc6fea00000 | -228    GB | ffffffc6feffffff |    6 MB | fixmap

   ffffffc6ff000000 | -228    GB | ffffffc6ffffffff |   16 MB | PCI io

   ffffffc700000000 | -228    GB | ffffffc7ffffffff |    4 GB | vmemmap

   ffffffc800000000 | -224    GB | ffffffd7ffffffff |   64 GB | vmalloc/ioremap space
@@ -83,7 +83,7 @@ RISC-V Linux Kernel SV48 
                                                              | Kernel-space virtual memory, shared between all processes:

  ____________________________________________________________|___________________________________________________________

                    |            |                  |         |

   ffff8d7ffee00000 |  -114.5 TB | ffff8d7ffeffffff |    2 MB | fixmap

   ffff8d7ffea00000 |  -114.5 TB | ffff8d7ffeffffff |    6 MB | fixmap

   ffff8d7fff000000 |  -114.5 TB | ffff8d7fffffffff |   16 MB | PCI io

   ffff8d8000000000 |  -114.5 TB | ffff8f7fffffffff |    2 TB | vmemmap

   ffff8f8000000000 |  -112.5 TB | ffffaf7fffffffff |   32 TB | vmalloc/ioremap space
@@ -119,7 +119,7 @@ RISC-V Linux Kernel SV57 
                                                              | Kernel-space virtual memory, shared between all processes:

  ____________________________________________________________|___________________________________________________________

                    |            |                  |         |

   ff1bfffffee00000 | -57     PB | ff1bfffffeffffff |    2 MB | fixmap

   ff1bfffffea00000 | -57     PB | ff1bfffffeffffff |    6 MB | fixmap

   ff1bffffff000000 | -57     PB | ff1bffffffffffff |   16 MB | PCI io

   ff1c000000000000 | -57     PB | ff1fffffffffffff |    1 PB | vmemmap

   ff20000000000000 | -56     PB | ff5fffffffffffff |   16 PB | vmalloc/ioremap space

arch/riscv/include/asm/fixmap.h

+8 −0
Original line number Diff line number Diff line
@@ -22,6 +22,14 @@ 
 */

enum fixed_addresses {

	FIX_HOLE,

	/*

	 * The fdt fixmap mapping must be PMD aligned and will be mapped

	 * using PMD entries in fixmap_pmd in 64-bit and a PGD entry in 32-bit.

	 */

	FIX_FDT_END,

	FIX_FDT = FIX_FDT_END + FIX_FDT_SIZE / PAGE_SIZE - 1,



	/* Below fixmaps will be mapped using fixmap_pte */

	FIX_PTE,

	FIX_PMD,

	FIX_PUD,

arch/riscv/include/asm/pgtable.h

+6 −2
Original line number Diff line number Diff line
@@ -87,9 +87,13 @@ 


#define FIXADDR_TOP      PCI_IO_START

#ifdef CONFIG_64BIT

#define FIXADDR_SIZE     PMD_SIZE

#define MAX_FDT_SIZE	 PMD_SIZE

#define FIX_FDT_SIZE	 (MAX_FDT_SIZE + SZ_2M)

#define FIXADDR_SIZE     (PMD_SIZE + FIX_FDT_SIZE)

#else

#define FIXADDR_SIZE     PGDIR_SIZE

#define MAX_FDT_SIZE	 PGDIR_SIZE

#define FIX_FDT_SIZE	 MAX_FDT_SIZE

#define FIXADDR_SIZE     (PGDIR_SIZE + FIX_FDT_SIZE)

#endif

#define FIXADDR_START    (FIXADDR_TOP - FIXADDR_SIZE)

arch/riscv/kernel/setup.c

+0 −1
Original line number Diff line number Diff line
@@ -283,7 +283,6 @@ void __init setup_arch(char **cmdline_p) 
	else

		pr_err("No DTB found in kernel mappings\n");

#endif

	early_init_fdt_scan_reserved_mem();

	misc_mem_init();



	init_resources();

arch/riscv/mm/init.c

+34 −27
Original line number Diff line number Diff line
@@ -57,7 +57,6 @@ unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)] 
EXPORT_SYMBOL(empty_zero_page);



extern char _start[];

#define DTB_EARLY_BASE_VA      PGDIR_SIZE

void *_dtb_early_va __initdata;

uintptr_t _dtb_early_pa __initdata;
@@ -236,6 +235,14 @@ static void __init setup_bootmem(void) 
	set_max_mapnr(max_low_pfn - ARCH_PFN_OFFSET);



	reserve_initrd_mem();



	/*

	 * No allocation should be done before reserving the memory as defined

	 * in the device tree, otherwise the allocation could end up in a

	 * reserved region.

	 */

	early_init_fdt_scan_reserved_mem();



	/*

	 * If DTB is built in, no need to reserve its memblock.

	 * Otherwise, do reserve it but avoid using
@@ -279,9 +286,6 @@ pgd_t trampoline_pg_dir[PTRS_PER_PGD] __page_aligned_bss; 
static pte_t fixmap_pte[PTRS_PER_PTE] __page_aligned_bss;



pgd_t early_pg_dir[PTRS_PER_PGD] __initdata __aligned(PAGE_SIZE);

static p4d_t __maybe_unused early_dtb_p4d[PTRS_PER_P4D] __initdata __aligned(PAGE_SIZE);

static pud_t __maybe_unused early_dtb_pud[PTRS_PER_PUD] __initdata __aligned(PAGE_SIZE);

static pmd_t __maybe_unused early_dtb_pmd[PTRS_PER_PMD] __initdata __aligned(PAGE_SIZE);



#ifdef CONFIG_XIP_KERNEL

#define pt_ops			(*(struct pt_alloc_ops *)XIP_FIXUP(&pt_ops))
@@ -626,9 +630,6 @@ static void __init create_p4d_mapping(p4d_t *p4dp, 
#define trampoline_pgd_next	(pgtable_l5_enabled ?			\

		(uintptr_t)trampoline_p4d : (pgtable_l4_enabled ?	\

		(uintptr_t)trampoline_pud : (uintptr_t)trampoline_pmd))

#define early_dtb_pgd_next	(pgtable_l5_enabled ?			\

		(uintptr_t)early_dtb_p4d : (pgtable_l4_enabled ?	\

		(uintptr_t)early_dtb_pud : (uintptr_t)early_dtb_pmd))

#else

#define pgd_next_t		pte_t

#define alloc_pgd_next(__va)	pt_ops.alloc_pte(__va)
@@ -636,7 +637,6 @@ static void __init create_p4d_mapping(p4d_t *p4dp, 
#define create_pgd_next_mapping(__nextp, __va, __pa, __sz, __prot)	\

	create_pte_mapping(__nextp, __va, __pa, __sz, __prot)

#define fixmap_pgd_next		((uintptr_t)fixmap_pte)

#define early_dtb_pgd_next	((uintptr_t)early_dtb_pmd)

#define create_p4d_mapping(__pmdp, __va, __pa, __sz, __prot) do {} while(0)

#define create_pud_mapping(__pmdp, __va, __pa, __sz, __prot) do {} while(0)

#define create_pmd_mapping(__pmdp, __va, __pa, __sz, __prot) do {} while(0)
@@ -860,32 +860,28 @@ static void __init create_kernel_page_table(pgd_t *pgdir, bool early) 
 * this means 2 PMD entries whereas for 32-bit kernel, this is only 1 PGDIR

 * entry.

 */

static void __init create_fdt_early_page_table(pgd_t *pgdir, uintptr_t dtb_pa)

static void __init create_fdt_early_page_table(pgd_t *pgdir,

					       uintptr_t fix_fdt_va,

					       uintptr_t dtb_pa)

{

#ifndef CONFIG_BUILTIN_DTB

	uintptr_t pa = dtb_pa & ~(PMD_SIZE - 1);



	create_pgd_mapping(early_pg_dir, DTB_EARLY_BASE_VA,

			   IS_ENABLED(CONFIG_64BIT) ? early_dtb_pgd_next : pa,

			   PGDIR_SIZE,

			   IS_ENABLED(CONFIG_64BIT) ? PAGE_TABLE : PAGE_KERNEL);



	if (pgtable_l5_enabled)

		create_p4d_mapping(early_dtb_p4d, DTB_EARLY_BASE_VA,

				   (uintptr_t)early_dtb_pud, P4D_SIZE, PAGE_TABLE);



	if (pgtable_l4_enabled)

		create_pud_mapping(early_dtb_pud, DTB_EARLY_BASE_VA,

				   (uintptr_t)early_dtb_pmd, PUD_SIZE, PAGE_TABLE);

#ifndef CONFIG_BUILTIN_DTB

	/* Make sure the fdt fixmap address is always aligned on PMD size */

	BUILD_BUG_ON(FIX_FDT % (PMD_SIZE / PAGE_SIZE));



	if (IS_ENABLED(CONFIG_64BIT)) {

		create_pmd_mapping(early_dtb_pmd, DTB_EARLY_BASE_VA,

	/* In 32-bit only, the fdt lies in its own PGD */

	if (!IS_ENABLED(CONFIG_64BIT)) {

		create_pgd_mapping(early_pg_dir, fix_fdt_va,

				   pa, MAX_FDT_SIZE, PAGE_KERNEL);

	} else {

		create_pmd_mapping(fixmap_pmd, fix_fdt_va,

				   pa, PMD_SIZE, PAGE_KERNEL);

		create_pmd_mapping(early_dtb_pmd, DTB_EARLY_BASE_VA + PMD_SIZE,

		create_pmd_mapping(fixmap_pmd, fix_fdt_va + PMD_SIZE,

				   pa + PMD_SIZE, PMD_SIZE, PAGE_KERNEL);

	}



	dtb_early_va = (void *)DTB_EARLY_BASE_VA + (dtb_pa & (PMD_SIZE - 1));

	dtb_early_va = (void *)fix_fdt_va + (dtb_pa & (PMD_SIZE - 1));

#else

	/*

	 * For 64-bit kernel, __va can't be used since it would return a linear
@@ -1055,7 +1051,8 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa) 
	create_kernel_page_table(early_pg_dir, true);



	/* Setup early mapping for FDT early scan */

	create_fdt_early_page_table(early_pg_dir, dtb_pa);

	create_fdt_early_page_table(early_pg_dir,

				    __fix_to_virt(FIX_FDT), dtb_pa);



	/*

	 * Bootime fixmap only can handle PMD_SIZE mapping. Thus, boot-ioremap
@@ -1097,6 +1094,16 @@ static void __init setup_vm_final(void) 
	u64 i;



	/* Setup swapper PGD for fixmap */

#if !defined(CONFIG_64BIT)

	/*

	 * In 32-bit, the device tree lies in a pgd entry, so it must be copied

	 * directly in swapper_pg_dir in addition to the pgd entry that points

	 * to fixmap_pte.

	 */

	unsigned long idx = pgd_index(__fix_to_virt(FIX_FDT));



	set_pgd(&swapper_pg_dir[idx], early_pg_dir[idx]);

#endif

	create_pgd_mapping(swapper_pg_dir, FIXADDR_START,

			   __pa_symbol(fixmap_pgd_next),

			   PGDIR_SIZE, PAGE_TABLE);