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| author | Palmer Dabbelt <palmer@rivosinc.com> | 2024-08-29 06:03:32 -0700 |
|---|---|---|
| committer | Palmer Dabbelt <palmer@rivosinc.com> | 2024-08-29 06:22:51 -0700 |
| commit | 84cfab9a1805f8e300e945f26e3fdff6d125bc20 (patch) | |
| tree | 1602481c9159dfc8e797cc1d6ed5292368b2e4cd /Documentation | |
| parent | 32d5f7add080a936e28ab4142bfeea6b06999789 (diff) | |
| parent | 2116988d5372aec51f8c4fb85bf8e305ecda47a0 (diff) | |
Merge patch series "riscv: mm: Do not restrict mmap address based on hint"
Charlie Jenkins <charlie@rivosinc.com> says:
There have been a couple of reports that using the hint address to
restrict the address returned by mmap hint address has caused issues in
applications. A different solution for restricting addresses returned by
mmap is necessary to avoid breakages.
[Palmer: This also just wasn't doing the right thing in the first place,
as it didn't handle the sv39 cases we were trying to deal with.]
* b4-shazam-merge:
riscv: mm: Do not restrict mmap address based on hint
riscv: selftests: Remove mmap hint address checks
Revert "RISC-V: mm: Document mmap changes"
Link: https://lore.kernel.org/r/20240826-riscv_mmap-v1-0-cd8962afe47f@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/arch/riscv/vm-layout.rst | 16 |
1 files changed, 0 insertions, 16 deletions
diff --git a/Documentation/arch/riscv/vm-layout.rst b/Documentation/arch/riscv/vm-layout.rst index 077b968dcc81..eabec99b5852 100644 --- a/Documentation/arch/riscv/vm-layout.rst +++ b/Documentation/arch/riscv/vm-layout.rst @@ -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`. |