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Revert "RISC-V: mm: Document mmap changes"

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This mmap behavior caused unintended breakages so the behavior has been
changed.

Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
Link: https://lore.kernel.org/r/20240826-riscv_mmap-v1-1-cd8962afe47f@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
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Charlie Jenkins 2024-08-26 09:36:45 -07:00 committed by Palmer Dabbelt
parent 8400291e28
commit 954260ff5a
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Documentation/arch/riscv/vm-layout.rst
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@ -134,19 +134,3 @@ RISC-V Linux Kernel SV57
ffffffff00000000 | -4 GB | ffffffff7fffffff | 2 GB | modules, BPF
ffffffff80000000 | -2 GB | ffffffffffffffff | 2 GB | kernel
__________________|____________|__________________|_________|____________________________________________________________
Userspace VAs
--------------------
To maintain compatibility with software that relies on the VA space with a
maximum of 48 bits the kernel will, by default, return virtual addresses to
userspace from a 48-bit range (sv48). This default behavior is achieved by
passing 0 into the hint address parameter of mmap. On CPUs with an address space
smaller than sv48, the CPU maximum supported address space will be the default.
Software can "opt-in" to receiving VAs from another VA space by providing
a hint address to mmap. When a hint address is passed to mmap, the returned
address will never use more bits than the hint address. For example, if a hint
address of `1 << 40` is passed to mmap, a valid returned address will never use
bits 41 through 63. If no mappable addresses are available in that range, mmap
will return `MAP_FAILED`.