diff options
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/admin-guide/kernel-parameters.txt | 8 | ||||
| -rw-r--r-- | Documentation/devicetree/bindings/riscv/cpus.yaml | 20 | ||||
| -rw-r--r-- | Documentation/riscv/hwprobe.rst | 13 | ||||
| -rw-r--r-- | Documentation/riscv/index.rst | 1 | ||||
| -rw-r--r-- | Documentation/riscv/vector.rst | 132 |
5 files changed, 163 insertions, 11 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 44bcaf791ce6..85fb0fa5d091 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -1,17 +1,17 @@ - acpi= [HW,ACPI,X86,ARM64] + acpi= [HW,ACPI,X86,ARM64,RISCV64] Advanced Configuration and Power Interface Format: { force | on | off | strict | noirq | rsdt | copy_dsdt } force -- enable ACPI if default was off - on -- enable ACPI but allow fallback to DT [arm64] + on -- enable ACPI but allow fallback to DT [arm64,riscv64] off -- disable ACPI if default was on noirq -- do not use ACPI for IRQ routing strict -- Be less tolerant of platforms that are not strictly ACPI specification compliant. rsdt -- prefer RSDT over (default) XSDT copy_dsdt -- copy DSDT to memory - For ARM64, ONLY "acpi=off", "acpi=on" or "acpi=force" - are available + For ARM64 and RISCV64, ONLY "acpi=off", "acpi=on" or + "acpi=force" are available See also Documentation/power/runtime_pm.rst, pci=noacpi diff --git a/Documentation/devicetree/bindings/riscv/cpus.yaml b/Documentation/devicetree/bindings/riscv/cpus.yaml index 3d2934b15e80..67bd239ead0b 100644 --- a/Documentation/devicetree/bindings/riscv/cpus.yaml +++ b/Documentation/devicetree/bindings/riscv/cpus.yaml @@ -23,6 +23,9 @@ description: | two cores, each of which has two hyperthreads, could be described as having four harts. +allOf: + - $ref: /schemas/cpu.yaml# + properties: compatible: oneOf: @@ -61,7 +64,7 @@ properties: hart. These values originate from the RISC-V Privileged Specification document, available from https://riscv.org/specifications/ - $ref: "/schemas/types.yaml#/definitions/string" + $ref: /schemas/types.yaml#/definitions/string enum: - riscv,sv32 - riscv,sv39 @@ -89,15 +92,18 @@ properties: Due to revisions of the ISA specification, some deviations have arisen over time. Notably, riscv,isa was defined prior to the creation of the - Zicsr and Zifencei extensions and thus "i" implies - "zicsr_zifencei". + Zicntr, Zicsr, Zifencei and Zihpm extensions and thus "i" + implies "zicntr_zicsr_zifencei_zihpm". While the isa strings in ISA specification are case insensitive, letters in the riscv,isa string must be all - lowercase to simplify parsing. - $ref: "/schemas/types.yaml#/definitions/string" + lowercase. + $ref: /schemas/types.yaml#/definitions/string pattern: ^rv(?:64|32)imaf?d?q?c?b?k?j?p?v?h?(?:[hsxz](?:[a-z])+)?(?:_[hsxz](?:[a-z])+)*$ + # RISC-V has multiple properties for cache op block sizes as the sizes + # differ between individual CBO extensions + cache-op-block-size: false # RISC-V requires 'timebase-frequency' in /cpus, so disallow it here timebase-frequency: false @@ -120,7 +126,7 @@ properties: - interrupt-controller cpu-idle-states: - $ref: '/schemas/types.yaml#/definitions/phandle-array' + $ref: /schemas/types.yaml#/definitions/phandle-array items: maxItems: 1 description: | @@ -137,7 +143,7 @@ required: - riscv,isa - interrupt-controller -additionalProperties: true +unevaluatedProperties: false examples: - | diff --git a/Documentation/riscv/hwprobe.rst b/Documentation/riscv/hwprobe.rst index 9f0dd62dcb5d..19165ebd82ba 100644 --- a/Documentation/riscv/hwprobe.rst +++ b/Documentation/riscv/hwprobe.rst @@ -64,6 +64,19 @@ The following keys are defined: * :c:macro:`RISCV_HWPROBE_IMA_C`: The C extension is supported, as defined by version 2.2 of the RISC-V ISA manual. + * :c:macro:`RISCV_HWPROBE_IMA_V`: The V extension is supported, as defined by + version 1.0 of the RISC-V Vector extension manual. + + * :c:macro:`RISCV_HWPROBE_EXT_ZBA`: The Zba address generation extension is + supported, as defined in version 1.0 of the Bit-Manipulation ISA + extensions. + + * :c:macro:`RISCV_HWPROBE_EXT_ZBB`: The Zbb extension is supported, as defined + in version 1.0 of the Bit-Manipulation ISA extensions. + + * :c:macro:`RISCV_HWPROBE_EXT_ZBS`: The Zbs extension is supported, as defined + in version 1.0 of the Bit-Manipulation ISA extensions. + * :c:macro:`RISCV_HWPROBE_KEY_CPUPERF_0`: A bitmask that contains performance information about the selected set of processors. diff --git a/Documentation/riscv/index.rst b/Documentation/riscv/index.rst index 175a91db0200..95cf9c1e1da1 100644 --- a/Documentation/riscv/index.rst +++ b/Documentation/riscv/index.rst @@ -10,6 +10,7 @@ RISC-V architecture hwprobe patch-acceptance uabi + vector features diff --git a/Documentation/riscv/vector.rst b/Documentation/riscv/vector.rst new file mode 100644 index 000000000000..48f189d79e41 --- /dev/null +++ b/Documentation/riscv/vector.rst @@ -0,0 +1,132 @@ +.. SPDX-License-Identifier: GPL-2.0 + +========================================= +Vector Extension Support for RISC-V Linux +========================================= + +This document briefly outlines the interface provided to userspace by Linux in +order to support the use of the RISC-V Vector Extension. + +1. prctl() Interface +--------------------- + +Two new prctl() calls are added to allow programs to manage the enablement +status for the use of Vector in userspace. The intended usage guideline for +these interfaces is to give init systems a way to modify the availability of V +for processes running under its domain. Calling thess interfaces is not +recommended in libraries routines because libraries should not override policies +configured from the parant process. Also, users must noted that these interfaces +are not portable to non-Linux, nor non-RISC-V environments, so it is discourage +to use in a portable code. To get the availability of V in an ELF program, +please read :c:macro:`COMPAT_HWCAP_ISA_V` bit of :c:macro:`ELF_HWCAP` in the +auxiliary vector. + +* prctl(PR_RISCV_V_SET_CONTROL, unsigned long arg) + + Sets the Vector enablement status of the calling thread, where the control + argument consists of two 2-bit enablement statuses and a bit for inheritance + mode. Other threads of the calling process are unaffected. + + Enablement status is a tri-state value each occupying 2-bit of space in + the control argument: + + * :c:macro:`PR_RISCV_V_VSTATE_CTRL_DEFAULT`: Use the system-wide default + enablement status on execve(). The system-wide default setting can be + controlled via sysctl interface (see sysctl section below). + + * :c:macro:`PR_RISCV_V_VSTATE_CTRL_ON`: Allow Vector to be run for the + thread. + + * :c:macro:`PR_RISCV_V_VSTATE_CTRL_OFF`: Disallow Vector. Executing Vector + instructions under such condition will trap and casuse the termination of the thread. + + arg: The control argument is a 5-bit value consisting of 3 parts, and + accessed by 3 masks respectively. + + The 3 masks, PR_RISCV_V_VSTATE_CTRL_CUR_MASK, + PR_RISCV_V_VSTATE_CTRL_NEXT_MASK, and PR_RISCV_V_VSTATE_CTRL_INHERIT + represents bit[1:0], bit[3:2], and bit[4]. bit[1:0] accounts for the + enablement status of current thread, and the setting at bit[3:2] takes place + at next execve(). bit[4] defines the inheritance mode of the setting in + bit[3:2]. + + * :c:macro:`PR_RISCV_V_VSTATE_CTRL_CUR_MASK`: bit[1:0]: Account for the + Vector enablement status for the calling thread. The calling thread is + not able to turn off Vector once it has been enabled. The prctl() call + fails with EPERM if the value in this mask is PR_RISCV_V_VSTATE_CTRL_OFF + but the current enablement status is not off. Setting + PR_RISCV_V_VSTATE_CTRL_DEFAULT here takes no effect but to set back + the original enablement status. + + * :c:macro:`PR_RISCV_V_VSTATE_CTRL_NEXT_MASK`: bit[3:2]: Account for the + Vector enablement setting for the calling thread at the next execve() + system call. If PR_RISCV_V_VSTATE_CTRL_DEFAULT is used in this mask, + then the enablement status will be decided by the system-wide + enablement status when execve() happen. + + * :c:macro:`PR_RISCV_V_VSTATE_CTRL_INHERIT`: bit[4]: the inheritance + mode for the setting at PR_RISCV_V_VSTATE_CTRL_NEXT_MASK. If the bit + is set then the following execve() will not clear the setting in both + PR_RISCV_V_VSTATE_CTRL_NEXT_MASK and PR_RISCV_V_VSTATE_CTRL_INHERIT. + This setting persists across changes in the system-wide default value. + + Return value: + * 0 on success; + * EINVAL: Vector not supported, invalid enablement status for current or + next mask; + * EPERM: Turning off Vector in PR_RISCV_V_VSTATE_CTRL_CUR_MASK if Vector + was enabled for the calling thread. + + On success: + * A valid setting for PR_RISCV_V_VSTATE_CTRL_CUR_MASK takes place + immediately. The enablement status specified in + PR_RISCV_V_VSTATE_CTRL_NEXT_MASK happens at the next execve() call, or + all following execve() calls if PR_RISCV_V_VSTATE_CTRL_INHERIT bit is + set. + * Every successful call overwrites a previous setting for the calling + thread. + +* prctl(PR_RISCV_V_GET_CONTROL) + + Gets the same Vector enablement status for the calling thread. Setting for + next execve() call and the inheritance bit are all OR-ed together. + + Note that ELF programs are able to get the availability of V for itself by + reading :c:macro:`COMPAT_HWCAP_ISA_V` bit of :c:macro:`ELF_HWCAP` in the + auxiliary vector. + + Return value: + * a nonnegative value on success; + * EINVAL: Vector not supported. + +2. System runtime configuration (sysctl) +----------------------------------------- + +To mitigate the ABI impact of expansion of the signal stack, a +policy mechanism is provided to the administrators, distro maintainers, and +developers to control the default Vector enablement status for userspace +processes in form of sysctl knob: + +* /proc/sys/abi/riscv_v_default_allow + + Writing the text representation of 0 or 1 to this file sets the default + system enablement status for new starting userspace programs. Valid values + are: + + * 0: Do not allow Vector code to be executed as the default for new processes. + * 1: Allow Vector code to be executed as the default for new processes. + + Reading this file returns the current system default enablement status. + + At every execve() call, a new enablement status of the new process is set to + the system default, unless: + + * PR_RISCV_V_VSTATE_CTRL_INHERIT is set for the calling process, and the + setting in PR_RISCV_V_VSTATE_CTRL_NEXT_MASK is not + PR_RISCV_V_VSTATE_CTRL_DEFAULT. Or, + + * The setting in PR_RISCV_V_VSTATE_CTRL_NEXT_MASK is not + PR_RISCV_V_VSTATE_CTRL_DEFAULT. + + Modifying the system default enablement status does not affect the enablement + status of any existing process of thread that do not make an execve() call. |