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Currently, RISC-V reserves 1MB of fixmap memory for device tree. However, it maps only single PMD (2MB) space for fixmap which leaves only < 1MB space left for other kernel features such as early ioremap which requires fixmap as well. The fixmap size can be increased by another 2MB but it brings additional complexity and changes the virtual memory layout as well. If we require some additional feature requiring fixmap again, it has to be moved again. Technically, DT doesn't need a fixmap as the memory occupied by the DT is only used during boot. That's why, We map device tree in early page table using two consecutive PGD mappings at lower addresses (< PAGE_OFFSET). This frees lot of space in fixmap and also makes maximum supported device tree size supported as PGDIR_SIZE. Thus, init memory section can be used for the same purpose as well. This simplifies fixmap implementation. Signed-off-by: Anup Patel <anup.patel@wdc.com> Signed-off-by: Atish Patra <atish.patra@wdc.com> Reviewed-by: Palmer Dabbelt <palmerdabbelt@google.com> Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>
20 lines
416 B
C
20 lines
416 B
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* Copyright (C) 2019 SiFive, Inc.
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*/
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#ifndef __ASM_HEAD_H
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#define __ASM_HEAD_H
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#include <linux/linkage.h>
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#include <linux/init.h>
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extern atomic_t hart_lottery;
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asmlinkage void do_page_fault(struct pt_regs *regs);
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asmlinkage void __init setup_vm(uintptr_t dtb_pa);
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extern void *__cpu_up_stack_pointer[];
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extern void *__cpu_up_task_pointer[];
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#endif /* __ASM_HEAD_H */
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