diff options
Diffstat (limited to 'Documentation/arch/riscv')
| -rw-r--r-- | Documentation/arch/riscv/hwprobe.rst | 36 | ||||
| -rw-r--r-- | Documentation/arch/riscv/vm-layout.rst | 16 |
2 files changed, 22 insertions, 30 deletions
diff --git a/Documentation/arch/riscv/hwprobe.rst b/Documentation/arch/riscv/hwprobe.rst index 3db60a0911df..85b709257918 100644 --- a/Documentation/arch/riscv/hwprobe.rst +++ b/Documentation/arch/riscv/hwprobe.rst @@ -239,25 +239,33 @@ The following keys are defined: ratified in commit 98918c844281 ("Merge pull request #1217 from riscv/zawrs") of riscv-isa-manual. -* :c:macro:`RISCV_HWPROBE_KEY_CPUPERF_0`: A bitmask that contains performance - information about the selected set of processors. +* :c:macro:`RISCV_HWPROBE_KEY_CPUPERF_0`: Deprecated. Returns similar values to + :c:macro:`RISCV_HWPROBE_KEY_MISALIGNED_SCALAR_PERF`, but the key was + mistakenly classified as a bitmask rather than a value. - * :c:macro:`RISCV_HWPROBE_MISALIGNED_UNKNOWN`: The performance of misaligned - accesses is unknown. +* :c:macro:`RISCV_HWPROBE_KEY_MISALIGNED_SCALAR_PERF`: An enum value describing + the performance of misaligned scalar native word accesses on the selected set + of processors. - * :c:macro:`RISCV_HWPROBE_MISALIGNED_EMULATED`: Misaligned accesses are - emulated via software, either in or below the kernel. These accesses are - always extremely slow. + * :c:macro:`RISCV_HWPROBE_MISALIGNED_SCALAR_UNKNOWN`: The performance of + misaligned scalar accesses is unknown. - * :c:macro:`RISCV_HWPROBE_MISALIGNED_SLOW`: Misaligned accesses are slower - than equivalent byte accesses. Misaligned accesses may be supported - directly in hardware, or trapped and emulated by software. + * :c:macro:`RISCV_HWPROBE_MISALIGNED_SCALAR_EMULATED`: Misaligned scalar + accesses are emulated via software, either in or below the kernel. These + accesses are always extremely slow. - * :c:macro:`RISCV_HWPROBE_MISALIGNED_FAST`: Misaligned accesses are faster - than equivalent byte accesses. + * :c:macro:`RISCV_HWPROBE_MISALIGNED_SCALAR_SLOW`: Misaligned scalar native + word sized accesses are slower than the equivalent quantity of byte + accesses. Misaligned accesses may be supported directly in hardware, or + trapped and emulated by software. - * :c:macro:`RISCV_HWPROBE_MISALIGNED_UNSUPPORTED`: Misaligned accesses are - not supported at all and will generate a misaligned address fault. + * :c:macro:`RISCV_HWPROBE_MISALIGNED_SCALAR_FAST`: Misaligned scalar native + word sized accesses are faster than the equivalent quantity of byte + accesses. + + * :c:macro:`RISCV_HWPROBE_MISALIGNED_SCALAR_UNSUPPORTED`: Misaligned scalar + accesses are not supported at all and will generate a misaligned address + fault. * :c:macro:`RISCV_HWPROBE_KEY_ZICBOZ_BLOCK_SIZE`: An unsigned int which represents the size of the Zicboz block in bytes. 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`. |