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| author | Andrew Jones <ajones@ventanamicro.com> | 2023-11-22 17:47:04 +0100 |
|---|---|---|
| committer | Palmer Dabbelt <palmer@rivosinc.com> | 2024-01-03 12:36:49 +0100 |
| commit | e178bf146e4b8c774a7b00aa2419e400f4f7894f (patch) | |
| tree | 23cdfbc75b8f05af3034171cb06833900268be79 /Documentation/arch/riscv/hwprobe.rst | |
| parent | RISC-V: Move the hwprobe syscall to its own file (diff) | |
| download | linux-e178bf146e4b8c774a7b00aa2419e400f4f7894f.tar.xz linux-e178bf146e4b8c774a7b00aa2419e400f4f7894f.zip | |
RISC-V: hwprobe: Introduce which-cpus flag
Introduce the first flag for the hwprobe syscall. The flag basically
reverses its behavior, i.e. instead of populating the values of keys
for a given set of cpus, the set of cpus after the call is the result
of finding a set which supports the values of the keys. In order to
do this, we implement a pair compare function which takes the type of
value (a single value vs. a bitmask of booleans) into consideration.
We also implement vdso support for the new flag.
Signed-off-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Evan Green <evan@rivosinc.com>
Link: https://lore.kernel.org/r/20231122164700.127954-9-ajones@ventanamicro.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Diffstat (limited to 'Documentation/arch/riscv/hwprobe.rst')
| -rw-r--r-- | Documentation/arch/riscv/hwprobe.rst | 17 |
1 files changed, 15 insertions, 2 deletions
diff --git a/Documentation/arch/riscv/hwprobe.rst b/Documentation/arch/riscv/hwprobe.rst index 132e9acaa8f4..12f9b0a043ac 100644 --- a/Documentation/arch/riscv/hwprobe.rst +++ b/Documentation/arch/riscv/hwprobe.rst @@ -25,8 +25,21 @@ arch, impl), the returned value will only be valid if all CPUs in the given set have the same value. Otherwise -1 will be returned. For boolean-like keys, the value returned will be a logical AND of the values for the specified CPUs. Usermode can supply NULL for ``cpus`` and 0 for ``cpusetsize`` as a shortcut for -all online CPUs. There are currently no flags, this value must be zero for -future compatibility. +all online CPUs. The currently supported flags are: + +* :c:macro:`RISCV_HWPROBE_WHICH_CPUS`: This flag basically reverses the behavior + of sys_riscv_hwprobe(). Instead of populating the values of keys for a given + set of CPUs, the values of each key are given and the set of CPUs is reduced + by sys_riscv_hwprobe() to only those which match each of the key-value pairs. + How matching is done depends on the key type. For value-like keys, matching + means to be the exact same as the value. For boolean-like keys, matching + means the result of a logical AND of the pair's value with the CPU's value is + exactly the same as the pair's value. Additionally, when ``cpus`` is an empty + set, then it is initialized to all online CPUs which fit within it, i.e. the + CPU set returned is the reduction of all the online CPUs which can be + represented with a CPU set of size ``cpusetsize``. + +All other flags are reserved for future compatibility and must be zero. On success 0 is returned, on failure a negative error code is returned. |