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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>
83 lines
1.8 KiB
C
83 lines
1.8 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* Copyright (C) 2009 Sunplus Core Technology Co., Ltd.
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* Chen Liqin <liqin.chen@sunplusct.com>
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* Lennox Wu <lennox.wu@sunplusct.com>
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* Copyright (C) 2012 Regents of the University of California
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*/
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#include <linux/init.h>
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#include <linux/mm.h>
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#include <linux/memblock.h>
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#include <linux/sched.h>
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#include <linux/console.h>
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#include <linux/screen_info.h>
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#include <linux/of_fdt.h>
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#include <linux/of_platform.h>
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#include <linux/sched/task.h>
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#include <linux/swiotlb.h>
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#include <asm/setup.h>
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#include <asm/sections.h>
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#include <asm/pgtable.h>
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#include <asm/smp.h>
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#include <asm/tlbflush.h>
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#include <asm/thread_info.h>
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#ifdef CONFIG_DUMMY_CONSOLE
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struct screen_info screen_info = {
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.orig_video_lines = 30,
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.orig_video_cols = 80,
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.orig_video_mode = 0,
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.orig_video_ega_bx = 0,
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.orig_video_isVGA = 1,
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.orig_video_points = 8
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};
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#endif
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/* The lucky hart to first increment this variable will boot the other cores */
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atomic_t hart_lottery;
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unsigned long boot_cpu_hartid;
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void __init parse_dtb(void)
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{
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if (early_init_dt_scan(dtb_early_va))
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return;
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pr_err("No DTB passed to the kernel\n");
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#ifdef CONFIG_CMDLINE_FORCE
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strlcpy(boot_command_line, CONFIG_CMDLINE, COMMAND_LINE_SIZE);
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pr_info("Forcing kernel command line to: %s\n", boot_command_line);
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#endif
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}
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void __init setup_arch(char **cmdline_p)
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{
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init_mm.start_code = (unsigned long) _stext;
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init_mm.end_code = (unsigned long) _etext;
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init_mm.end_data = (unsigned long) _edata;
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init_mm.brk = (unsigned long) _end;
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*cmdline_p = boot_command_line;
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parse_early_param();
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setup_bootmem();
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paging_init();
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unflatten_device_tree();
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#ifdef CONFIG_SWIOTLB
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swiotlb_init(1);
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#endif
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#ifdef CONFIG_SMP
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setup_smp();
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#endif
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#ifdef CONFIG_DUMMY_CONSOLE
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conswitchp = &dummy_con;
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#endif
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riscv_fill_hwcap();
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}
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