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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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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>
82 lines
1.8 KiB
C
82 lines
1.8 KiB
C
/* SPDX-License-Identifier: GPL-2.0-only */
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/*
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* Copyright (C) 2012 Regents of the University of California
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*/
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#ifndef _ASM_RISCV_PGTABLE_64_H
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#define _ASM_RISCV_PGTABLE_64_H
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#include <linux/const.h>
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#define PGDIR_SHIFT 30
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/* Size of region mapped by a page global directory */
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#define PGDIR_SIZE (_AC(1, UL) << PGDIR_SHIFT)
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#define PGDIR_MASK (~(PGDIR_SIZE - 1))
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#define PMD_SHIFT 21
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/* Size of region mapped by a page middle directory */
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#define PMD_SIZE (_AC(1, UL) << PMD_SHIFT)
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#define PMD_MASK (~(PMD_SIZE - 1))
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/* Page Middle Directory entry */
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typedef struct {
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unsigned long pmd;
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} pmd_t;
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#define pmd_val(x) ((x).pmd)
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#define __pmd(x) ((pmd_t) { (x) })
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#define PTRS_PER_PMD (PAGE_SIZE / sizeof(pmd_t))
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static inline int pud_present(pud_t pud)
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{
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return (pud_val(pud) & _PAGE_PRESENT);
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}
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static inline int pud_none(pud_t pud)
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{
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return (pud_val(pud) == 0);
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}
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static inline int pud_bad(pud_t pud)
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{
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return !pud_present(pud);
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}
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static inline void set_pud(pud_t *pudp, pud_t pud)
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{
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*pudp = pud;
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}
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static inline void pud_clear(pud_t *pudp)
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{
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set_pud(pudp, __pud(0));
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}
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static inline unsigned long pud_page_vaddr(pud_t pud)
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{
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return (unsigned long)pfn_to_virt(pud_val(pud) >> _PAGE_PFN_SHIFT);
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}
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#define pmd_index(addr) (((addr) >> PMD_SHIFT) & (PTRS_PER_PMD - 1))
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static inline pmd_t *pmd_offset(pud_t *pud, unsigned long addr)
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{
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return (pmd_t *)pud_page_vaddr(*pud) + pmd_index(addr);
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}
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static inline pmd_t pfn_pmd(unsigned long pfn, pgprot_t prot)
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{
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return __pmd((pfn << _PAGE_PFN_SHIFT) | pgprot_val(prot));
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}
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static inline unsigned long _pmd_pfn(pmd_t pmd)
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{
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return pmd_val(pmd) >> _PAGE_PFN_SHIFT;
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}
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#define pmd_ERROR(e) \
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pr_err("%s:%d: bad pmd %016lx.\n", __FILE__, __LINE__, pmd_val(e))
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#endif /* _ASM_RISCV_PGTABLE_64_H */
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