[PATCH v4 00/16] riscv: Support vendor extensions and xtheadvector

Charlie Jenkins
2024-04-26T21:29:25Z

This patch series ended up much larger than expected, please bear with
me! The goal here is to support vendor extensions, starting at probing
the device tree and ending with reporting to userspace.

The main design objective was to allow vendors to operate independently
of each other. This has been achieved by delegating vendor extensions to
a their own files and then accumulating the extensions in
arch/riscv/kernel/vendor_extensions.c.

Each vendor will have their own list of extensions they support.

There is a new hwprobe key RISCV_HWPROBE_KEY_VENDOR_EXT_THEAD_0 that is
used to request which thead vendor extensions are supported on the
current platform. This allows future vendors to allocate hwprobe keys
for their vendor.

On to the xtheadvector specific code. xtheadvector is a custom extension
that is based upon riscv vector version 0.7.1 [1]. All of the vector
routines have been modified to support this alternative vector version
based upon whether xtheadvector was determined to be supported at boot.
I have tested this with an Allwinner Nezha board. I ran into issues
booting the board on 6.9-rc1 so I applied these patches to 6.8. There
are a couple of minor merge conflicts that do arrise when doing that, so
please let me know if you have been able to boot this board with a 6.9
kernel. I used SkiffOS [2] to manage building the image, but upgraded
the U-Boot version to Samuel Holland's more up-to-date version [3] and
changed out the device tree used by U-Boot with the device trees that
are present in upstream linux and this series. Thank you Samuel for all
of the work you did to make this task possible.

To test the integration, I used the riscv vector kselftests. I modified
the test cases to be able to more easily extend them, and then added a
xtheadvector target that works by calling hwprobe and swapping out the
vector asm if needed.

[1] https://github.com/T-head-Semi/thead-extension-spec/blob/95358cb2cca9489361c61d335e03d3134b14133f/xtheadvector.adoc
[2] https://github.com/skiffos/SkiffOS/tree/master/configs/allwinner/nezha
[3] https://github.com/smaeul/u-boot/commit/2e89b706f5c956a70c989cd31665f1429e9a0b48

Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
---
Changes in v4:
- Disable vector immediately if vlenb from the device tree is not
homogeneous
- Hide vendor extension code behind a hidden config that vendor
extensions select to eliminate the code when kernel is compiled
without vendor extensions
- Clear up naming conventions and introduce some defines to make the
vendor extension code clearer
- Link to v3: https://lore.kernel.org/r/20240420-dev-charlie-support_thead_vector_6_9-v3-0-67cff4271d1d@rivosinc.com

Changes in v3:
- Allow any hardware to support any vendor extension, rather than
restricting the vendor extensions to the same vendor as the hardware
- Introduce config options to enable/disable a vendor's extensions
- Link to v2: https://lore.kernel.org/r/20240415-dev-charlie-support_thead_vector_6_9-v2-0-c7d68c603268@rivosinc.com

Changes in v2:
- Added commit hash to xtheadvector
- Simplified riscv,isa vector removal fix to not mess with the DT
riscv,vendorid
- Moved riscv,vendorid parsing into a different patch and cache the
value to be used by alternative patching
- Reduce riscv,vendorid missing severity to "info"
- Separate vendor extension list to vendor files
- xtheadvector no longer puts v in the elf_hwcap
- Only patch vendor extension if all harts are associated with the same
vendor. This is the best chance the kernel has for working properly if
there are multiple vendors.
- Split hwprobe vendor keys out into vendor file
- Add attribution for Heiko's patches
- Link to v1: https://lore.kernel.org/r/20240411-dev-charlie-support_thead_vector_6_9-v1-0-4af9815ec746@rivosinc.com

---
Charlie Jenkins (14):
dt-bindings: riscv: Add xtheadvector ISA extension description
riscv: vector: Use vlenb from DT
riscv: dts: allwinner: Add xtheadvector to the D1/D1s devicetree
riscv: Extend cpufeature.c to detect vendor extensions
riscv: Introduce vendor variants of extension helpers
riscv: cpufeature: Extract common elements from extension checking
riscv: Convert xandespmu to use the vendor extension framework
riscv: csr: Add CSR encodings for VCSR_VXRM/VCSR_VXSAT
riscv: Add xtheadvector instruction definitions
riscv: vector: Support xtheadvector save/restore
riscv: hwprobe: Add thead vendor extension probing
riscv: hwprobe: Document thead vendor extensions and xtheadvector extension
selftests: riscv: Fix vector tests
selftests: riscv: Support xtheadvector in vector tests

Conor Dooley (1):
dt-bindings: riscv: cpus: add a vlen register length property

Heiko Stuebner (1):
RISC-V: define the elements of the VCSR vector CSR

Documentation/arch/riscv/hwprobe.rst | 10 +
Documentation/devicetree/bindings/riscv/cpus.yaml | 6 +
.../devicetree/bindings/riscv/extensions.yaml | 10 +
arch/riscv/Kconfig | 2 +
arch/riscv/Kconfig.vendor | 44 +++
arch/riscv/boot/dts/allwinner/sun20i-d1s.dtsi | 3 +-
arch/riscv/errata/andes/errata.c | 2 +
arch/riscv/errata/sifive/errata.c | 3 +
arch/riscv/errata/thead/errata.c | 3 +
arch/riscv/include/asm/cpufeature.h | 98 ++++---
arch/riscv/include/asm/csr.h | 13 +
arch/riscv/include/asm/hwcap.h | 1 -
arch/riscv/include/asm/hwprobe.h | 4 +-
arch/riscv/include/asm/switch_to.h | 2 +-
arch/riscv/include/asm/vector.h | 247 +++++++++++++----
arch/riscv/include/asm/vendor_extensions.h | 95 +++++++
arch/riscv/include/asm/vendor_extensions/andes.h | 19 ++
arch/riscv/include/asm/vendor_extensions/thead.h | 45 ++++
.../include/asm/vendor_extensions/thead_hwprobe.h | 11 +
arch/riscv/include/uapi/asm/hwprobe.h | 3 +-
arch/riscv/include/uapi/asm/vendor/thead.h | 3 +
arch/riscv/kernel/Makefile | 2 +
arch/riscv/kernel/cpufeature.c | 155 ++++++++---
arch/riscv/kernel/kernel_mode_vector.c | 8 +-
arch/riscv/kernel/process.c | 4 +-
arch/riscv/kernel/signal.c | 6 +-
arch/riscv/kernel/sys_hwprobe.c | 9 +
arch/riscv/kernel/vector.c | 25 +-
arch/riscv/kernel/vendor_extensions.c | 69 +++++
arch/riscv/kernel/vendor_extensions/Makefile | 5 +
arch/riscv/kernel/vendor_extensions/andes.c | 35 +++
arch/riscv/kernel/vendor_extensions/thead.c | 36 +++
.../riscv/kernel/vendor_extensions/thead_hwprobe.c | 42 +++
drivers/perf/riscv_pmu_sbi.c | 9 +-
tools/testing/selftests/riscv/vector/.gitignore | 3 +-
tools/testing/selftests/riscv/vector/Makefile | 17 +-
.../selftests/riscv/vector/v_exec_initval_nolibc.c | 93 +++++++
tools/testing/selftests/riscv/vector/v_helpers.c | 67 +++++
tools/testing/selftests/riscv/vector/v_helpers.h | 7 +
tools/testing/selftests/riscv/vector/v_initval.c | 22 ++
.../selftests/riscv/vector/v_initval_nolibc.c | 68 -----
.../selftests/riscv/vector/vstate_exec_nolibc.c | 20 +-
.../testing/selftests/riscv/vector/vstate_prctl.c | 295 ++++++++++++---------
43 files changed, 1283 insertions(+), 338 deletions(-)
---
base-commit: 4cece764965020c22cff7665b18a012006359095
change-id: 20240411-dev-charlie-support_thead_vector_6_9-1591fc2a431d
--
- Charlie