diff options
| author | Clément Léger <cleger@rivosinc.com> | 2024-04-10 16:45:57 +0200 |
|---|---|---|
| committer | Palmer Dabbelt <palmer@rivosinc.com> | 2024-07-11 08:57:33 -0700 |
| commit | c9b8cd139c1dfb95eb86fd6a58cfe2089843d1d4 (patch) | |
| tree | 60e0509f755dfbb1ebc22e52ec6b0a58fc756919 /Documentation/arch/riscv | |
| parent | 16badacd8af48980c546839626d0329bab32b4c3 (diff) | |
riscv: hwprobe: export highest virtual userspace address
Some userspace applications (OpenJDK for instance) uses the free MSBs
in pointers to insert additional information for their own logic and
need to get this information from somewhere. Currently they rely on
parsing /proc/cpuinfo "mmu=svxx" string to obtain the current value of
virtual address usable bits [1]. Since this reflect the raw supported
MMU mode, it might differ from the logical one used internally which is
why arch_get_mmap_end() is used. Exporting the highest mmapable address
through hwprobe will allow a more stable interface to be used. For that
purpose, add a new hwprobe key named
RISCV_HWPROBE_KEY_HIGHEST_VIRT_ADDRESS which will export the highest
userspace virtual address.
Link: https://github.com/openjdk/jdk/blob/master/src/hotspot/os_cpu/linux_riscv/vm_version_linux_riscv.cpp#L171 [1]
Signed-off-by: Clément Léger <cleger@rivosinc.com>
Reviewed-by: Charlie Jenkins <charlie@rivosinc.com>
Link: https://lore.kernel.org/r/20240410144558.1104006-1-cleger@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Diffstat (limited to 'Documentation/arch/riscv')
| -rw-r--r-- | Documentation/arch/riscv/hwprobe.rst | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/Documentation/arch/riscv/hwprobe.rst b/Documentation/arch/riscv/hwprobe.rst index 25d783be2878..652e6ef05baa 100644 --- a/Documentation/arch/riscv/hwprobe.rst +++ b/Documentation/arch/riscv/hwprobe.rst @@ -257,3 +257,6 @@ The following keys are defined: * :c:macro:`RISCV_HWPROBE_KEY_ZICBOZ_BLOCK_SIZE`: An unsigned int which represents the size of the Zicboz block in bytes. + +* :c:macro:`RISCV_HWPROBE_KEY_HIGHEST_VIRT_ADDRESS`: An unsigned long which + represent the highest userspace virtual address usable. |