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671f9a3e2e
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> |
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| .. | ||
| asm-offsets.h | ||
| asm-prototypes.h | ||
| asm.h | ||
| atomic.h | ||
| barrier.h | ||
| bitops.h | ||
| bug.h | ||
| cache.h | ||
| cacheflush.h | ||
| cmpxchg.h | ||
| csr.h | ||
| current.h | ||
| delay.h | ||
| elf.h | ||
| fence.h | ||
| fixmap.h | ||
| ftrace.h | ||
| futex.h | ||
| hugetlb.h | ||
| hwcap.h | ||
| io.h | ||
| irq.h | ||
| irqflags.h | ||
| Kbuild | ||
| kprobes.h | ||
| linkage.h | ||
| mmiowb.h | ||
| mmu_context.h | ||
| mmu.h | ||
| module.h | ||
| page.h | ||
| pci.h | ||
| perf_event.h | ||
| pgalloc.h | ||
| pgtable-32.h | ||
| pgtable-64.h | ||
| pgtable-bits.h | ||
| pgtable.h | ||
| processor.h | ||
| ptrace.h | ||
| sbi.h | ||
| sifive_l2_cache.h | ||
| smp.h | ||
| spinlock_types.h | ||
| spinlock.h | ||
| string.h | ||
| switch_to.h | ||
| syscall.h | ||
| thread_info.h | ||
| timex.h | ||
| tlb.h | ||
| tlbflush.h | ||
| uaccess.h | ||
| unistd.h | ||
| vdso.h | ||
| word-at-a-time.h | ||