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author | Anup Patel <Anup.Patel@wdc.com> | 2019-06-28 23:36:21 +0300 |
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committer | Paul Walmsley <paul.walmsley@sifive.com> | 2019-07-09 19:08:04 +0300 |
commit | 671f9a3e2e24cdeb2d2856abee7422f093e23e29 (patch) | |
tree | 12c0271582f801f9dc2b0a2be59ee891e6c5f99f /arch/riscv/include | |
parent | 2ebca1cbb4a5a31f8d89f22d9d410b432a97f7a7 (diff) | |
download | linux-671f9a3e2e24cdeb2d2856abee7422f093e23e29.tar.xz |
RISC-V: Setup initial page tables in two stages
Currently, the setup_vm() does initial page table setup in one-shot
very early before enabling MMU. Due to this, the setup_vm() has to map
all possible kernel virtual addresses since it does not know size and
location of RAM. This means we have kernel mappings for non-existent
RAM and any buggy driver (or kernel) code doing out-of-bound access
to RAM will not fault and cause underterministic behaviour.
Further, the setup_vm() creates PMD mappings (i.e. 2M mappings) for
RV64 systems. This means for PAGE_OFFSET=0xffffffe000000000 (i.e.
MAXPHYSMEM_128GB=y), the setup_vm() will require 129 pages (i.e.
516 KB) of memory for initial page tables which is never freed. The
memory required for initial page tables will further increase if
we chose a lower value of PAGE_OFFSET (e.g. 0xffffff0000000000)
This patch implements two-staged initial page table setup, as follows:
1. Early (i.e. setup_vm()): This stage maps kernel image and DTB in
a early page table (i.e. early_pg_dir). The early_pg_dir will be used
only by boot HART so it can be freed as-part of init memory free-up.
2. Final (i.e. setup_vm_final()): This stage maps all possible RAM
banks in the final page table (i.e. swapper_pg_dir). The boot HART
will start using swapper_pg_dir at the end of setup_vm_final(). All
non-boot HARTs directly use the swapper_pg_dir created by boot HART.
We have following advantages with this new approach:
1. Kernel mappings for non-existent RAM don't exists anymore.
2. Memory consumed by initial page tables is now indpendent of the
chosen PAGE_OFFSET.
3. Memory consumed by initial page tables on RV64 system is 2 pages
(i.e. 8 KB) which has significantly reduced and these pages will be
freed as-part of the init memory free-up.
The patch also provides a foundation for implementing strict kernel
mappings where we protect kernel text and rodata using PTE permissions.
Suggested-by: Mike Rapoport <rppt@linux.ibm.com>
Signed-off-by: Anup Patel <anup.patel@wdc.com>
[paul.walmsley@sifive.com: updated to apply; fixed a checkpatch warning]
Signed-off-by: Paul Walmsley <paul.walmsley@sifive.com>
Diffstat (limited to 'arch/riscv/include')
-rw-r--r-- | arch/riscv/include/asm/fixmap.h | 5 | ||||
-rw-r--r-- | arch/riscv/include/asm/pgtable-64.h | 5 | ||||
-rw-r--r-- | arch/riscv/include/asm/pgtable.h | 8 |
3 files changed, 18 insertions, 0 deletions
diff --git a/arch/riscv/include/asm/fixmap.h b/arch/riscv/include/asm/fixmap.h index c207f6634b91..9c66033c3a54 100644 --- a/arch/riscv/include/asm/fixmap.h +++ b/arch/riscv/include/asm/fixmap.h @@ -21,6 +21,11 @@ */ enum fixed_addresses { FIX_HOLE, +#define FIX_FDT_SIZE SZ_1M + FIX_FDT_END, + FIX_FDT = FIX_FDT_END + FIX_FDT_SIZE / PAGE_SIZE - 1, + FIX_PTE, + FIX_PMD, FIX_EARLYCON_MEM_BASE, __end_of_fixed_addresses }; diff --git a/arch/riscv/include/asm/pgtable-64.h b/arch/riscv/include/asm/pgtable-64.h index 45dfac2ac51f..74630989006d 100644 --- a/arch/riscv/include/asm/pgtable-64.h +++ b/arch/riscv/include/asm/pgtable-64.h @@ -70,6 +70,11 @@ static inline pmd_t pfn_pmd(unsigned long pfn, pgprot_t prot) return __pmd((pfn << _PAGE_PFN_SHIFT) | pgprot_val(prot)); } +static inline unsigned long _pmd_pfn(pmd_t pmd) +{ + return pmd_val(pmd) >> _PAGE_PFN_SHIFT; +} + #define pmd_ERROR(e) \ pr_err("%s:%d: bad pmd %016lx.\n", __FILE__, __LINE__, pmd_val(e)) diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h index 18ea56fabba8..a364aba23d55 100644 --- a/arch/riscv/include/asm/pgtable.h +++ b/arch/riscv/include/asm/pgtable.h @@ -59,6 +59,8 @@ #define PAGE_KERNEL __pgprot(_PAGE_KERNEL) #define PAGE_KERNEL_EXEC __pgprot(_PAGE_KERNEL | _PAGE_EXEC) +#define PAGE_TABLE __pgprot(_PAGE_TABLE) + extern pgd_t swapper_pg_dir[]; /* MAP_PRIVATE permissions: xwr (copy-on-write) */ @@ -118,6 +120,11 @@ static inline pgd_t pfn_pgd(unsigned long pfn, pgprot_t prot) return __pgd((pfn << _PAGE_PFN_SHIFT) | pgprot_val(prot)); } +static inline unsigned long _pgd_pfn(pgd_t pgd) +{ + return pgd_val(pgd) >> _PAGE_PFN_SHIFT; +} + #define pgd_index(addr) (((addr) >> PGDIR_SHIFT) & (PTRS_PER_PGD - 1)) /* Locate an entry in the page global directory */ @@ -400,6 +407,7 @@ static inline int ptep_clear_flush_young(struct vm_area_struct *vma, #define kern_addr_valid(addr) (1) /* FIXME */ #endif +extern void *dtb_early_va; extern void setup_bootmem(void); extern void paging_init(void); |