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riscv establishes 2 virtual mappings: - early_pg_dir maps the kernel which allows to discover the system memory - swapper_pg_dir installs the final mapping (linear mapping included) We used to map the dtb in early_pg_dir using DTB_EARLY_BASE_VA, and this mapping was not carried over in swapper_pg_dir. It happens that early_init_fdt_scan_reserved_mem() must be called before swapper_pg_dir is setup otherwise we could allocate reserved memory defined in the dtb. And this function initializes reserved_mem variable with addresses that lie in the early_pg_dir dtb mapping: when those addresses are reused with swapper_pg_dir, this mapping does not exist and then we trap. The previous "fix" was incorrect as early_init_fdt_scan_reserved_mem() must be called before swapper_pg_dir is set up otherwise we could allocate in reserved memory defined in the dtb. So move the dtb mapping in the fixmap region which is established in early_pg_dir and handed over to swapper_pg_dir. Fixes:922b0375fc("riscv: Fix memblock reservation for device tree blob") Fixes:8f3a2b4a96("RISC-V: Move DT mapping outof fixmap") Fixes:50e63dd8ed("riscv: fix reserved memory setup") Reported-by: Conor Dooley <conor.dooley@microchip.com> Link: https://lore.kernel.org/all/f8e67f82-103d-156c-deb0-d6d6e2756f5e@microchip.com/ Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com> Reviewed-by: Conor Dooley <conor.dooley@microchip.com> Tested-by: Conor Dooley <conor.dooley@microchip.com> Link: https://lore.kernel.org/r/20230329081932.79831-2-alexghiti@rivosinc.com Cc: stable@vger.kernel.org Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
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.. SPDX-License-Identifier: GPL-2.0
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=====================================
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Virtual Memory Layout on RISC-V Linux
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=====================================
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:Author: Alexandre Ghiti <alex@ghiti.fr>
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:Date: 12 February 2021
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This document describes the virtual memory layout used by the RISC-V Linux
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Kernel.
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RISC-V Linux Kernel 32bit
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=========================
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RISC-V Linux Kernel SV32
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------------------------
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TODO
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RISC-V Linux Kernel 64bit
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=========================
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The RISC-V privileged architecture document states that the 64bit addresses
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"must have bits 63–48 all equal to bit 47, or else a page-fault exception will
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occur.": that splits the virtual address space into 2 halves separated by a very
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big hole, the lower half is where the userspace resides, the upper half is where
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the RISC-V Linux Kernel resides.
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RISC-V Linux Kernel SV39
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------------------------
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::
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========================================================================================================================
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Start addr | Offset | End addr | Size | VM area description
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========================================================================================================================
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0000000000000000 | 0 | 0000003fffffffff | 256 GB | user-space virtual memory, different per mm
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__________________|____________|__________________|_________|___________________________________________________________
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| | | |
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0000004000000000 | +256 GB | ffffffbfffffffff | ~16M TB | ... huge, almost 64 bits wide hole of non-canonical
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| | | | virtual memory addresses up to the -256 GB
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| | | | starting offset of kernel mappings.
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__________________|____________|__________________|_________|___________________________________________________________
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| Kernel-space virtual memory, shared between all processes:
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____________________________________________________________|___________________________________________________________
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| | | |
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ffffffc6fea00000 | -228 GB | ffffffc6feffffff | 6 MB | fixmap
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ffffffc6ff000000 | -228 GB | ffffffc6ffffffff | 16 MB | PCI io
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ffffffc700000000 | -228 GB | ffffffc7ffffffff | 4 GB | vmemmap
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ffffffc800000000 | -224 GB | ffffffd7ffffffff | 64 GB | vmalloc/ioremap space
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ffffffd800000000 | -160 GB | fffffff6ffffffff | 124 GB | direct mapping of all physical memory
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fffffff700000000 | -36 GB | fffffffeffffffff | 32 GB | kasan
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__________________|____________|__________________|_________|____________________________________________________________
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____________________________________________________________|____________________________________________________________
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ffffffff00000000 | -4 GB | ffffffff7fffffff | 2 GB | modules, BPF
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ffffffff80000000 | -2 GB | ffffffffffffffff | 2 GB | kernel
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__________________|____________|__________________|_________|____________________________________________________________
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RISC-V Linux Kernel SV48
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------------------------
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::
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========================================================================================================================
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Start addr | Offset | End addr | Size | VM area description
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========================================================================================================================
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| | | |
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0000000000000000 | 0 | 00007fffffffffff | 128 TB | user-space virtual memory, different per mm
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__________________|____________|__________________|_________|___________________________________________________________
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0000800000000000 | +128 TB | ffff7fffffffffff | ~16M TB | ... huge, almost 64 bits wide hole of non-canonical
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| | | | virtual memory addresses up to the -128 TB
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| | | | starting offset of kernel mappings.
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__________________|____________|__________________|_________|___________________________________________________________
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| Kernel-space virtual memory, shared between all processes:
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____________________________________________________________|___________________________________________________________
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| | | |
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ffff8d7ffea00000 | -114.5 TB | ffff8d7ffeffffff | 6 MB | fixmap
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ffff8d7fff000000 | -114.5 TB | ffff8d7fffffffff | 16 MB | PCI io
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ffff8d8000000000 | -114.5 TB | ffff8f7fffffffff | 2 TB | vmemmap
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ffff8f8000000000 | -112.5 TB | ffffaf7fffffffff | 32 TB | vmalloc/ioremap space
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ffffaf8000000000 | -80.5 TB | ffffef7fffffffff | 64 TB | direct mapping of all physical memory
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ffffef8000000000 | -16.5 TB | fffffffeffffffff | 16.5 TB | kasan
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__________________|____________|__________________|_________|____________________________________________________________
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| Identical layout to the 39-bit one from here on:
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____________________________________________________________|____________________________________________________________
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ffffffff00000000 | -4 GB | ffffffff7fffffff | 2 GB | modules, BPF
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ffffffff80000000 | -2 GB | ffffffffffffffff | 2 GB | kernel
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__________________|____________|__________________|_________|____________________________________________________________
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RISC-V Linux Kernel SV57
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------------------------
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::
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========================================================================================================================
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Start addr | Offset | End addr | Size | VM area description
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========================================================================================================================
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| | | |
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0000000000000000 | 0 | 00ffffffffffffff | 64 PB | user-space virtual memory, different per mm
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__________________|____________|__________________|_________|___________________________________________________________
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| | | |
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0100000000000000 | +64 PB | feffffffffffffff | ~16K PB | ... huge, almost 64 bits wide hole of non-canonical
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| | | | virtual memory addresses up to the -64 PB
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| | | | starting offset of kernel mappings.
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__________________|____________|__________________|_________|___________________________________________________________
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| Kernel-space virtual memory, shared between all processes:
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____________________________________________________________|___________________________________________________________
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| | | |
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ff1bfffffea00000 | -57 PB | ff1bfffffeffffff | 6 MB | fixmap
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ff1bffffff000000 | -57 PB | ff1bffffffffffff | 16 MB | PCI io
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ff1c000000000000 | -57 PB | ff1fffffffffffff | 1 PB | vmemmap
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ff20000000000000 | -56 PB | ff5fffffffffffff | 16 PB | vmalloc/ioremap space
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ff60000000000000 | -40 PB | ffdeffffffffffff | 32 PB | direct mapping of all physical memory
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ffdf000000000000 | -8 PB | fffffffeffffffff | 8 PB | kasan
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__________________|____________|__________________|_________|____________________________________________________________
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| Identical layout to the 39-bit one from here on:
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____________________________________________________________|____________________________________________________________
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| | | |
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ffffffff00000000 | -4 GB | ffffffff7fffffff | 2 GB | modules, BPF
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ffffffff80000000 | -2 GB | ffffffffffffffff | 2 GB | kernel
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__________________|____________|__________________|_________|____________________________________________________________
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