[PATCH v10 00/14] riscv: Add support for xtheadvector

[Charlie Jenkins]

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.

vlenb is not supported on the existing xtheadvector hardware, so a
devicetree property thead,vlenb is added to provide the vlenb to Linux.

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.

Support for xtheadvector is also added to the vector kselftests.

Signed-off-by: Charlie Jenkins <charlie@xxxxxxxxxxxx>

[1] https://github.com/T-head-Semi/thead-extension-spec/blob/95358cb2cca9489361c61d335e03d3134b14133f/xtheadvector.adoc

---
This series is a continuation of a different series that was fragmented
into two other series in an attempt to get part of it merged in the 6.10
merge window. The split-off series did not get merged due to a NAK on
the series that added the generic riscv,vlenb devicetree entry. This
series has converted riscv,vlenb to thead,vlenb to remedy this issue.

The original series is titled "riscv: Support vendor extensions and
xtheadvector" [3].

The series titled "riscv: Extend cpufeature.c to detect vendor
extensions" is still under development and this series is based on that
series! [4]

I have tested this with an Allwinner Nezha board. I used SkiffOS [1] to
manage building the image, but upgraded the U-Boot version to Samuel
Holland's more up-to-date version [2] 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.

[1] https://github.com/skiffos/SkiffOS/tree/master/configs/allwinner/nezha
[2] https://github.com/smaeul/u-boot/commit/2e89b706f5c956a70c989cd31665f1429e9a0b48
[3] https://lore.kernel.org/all/20240503-dev-charlie-support_thead_vector_6_9-v6-0-cb7624e65d82@xxxxxxxxxxxx/
[4] https://lore.kernel.org/lkml/20240719-support_vendor_extensions-v3-4-0af7587bbec0@xxxxxxxxxxxx/T/

---
Changes in v10:
- In DT probing disable vector with new function to clear vendor
  extension bits for xtheadvector
- Add ghostwrite mitigations for c9xx CPUs. This disables xtheadvector
  unless mitigations=off is set as a kernel boot arg
- Link to v9: https://lore.kernel.org/r/20240806-xtheadvector-v9-0-62a56d2da5d0@xxxxxxxxxxxx

Changes in v9:
- Rebase onto palmer's for-next
- Fix sparse error in arch/riscv/kernel/vendor_extensions/thead.c
- Fix maybe-uninitialized warning in arch/riscv/include/asm/vendor_extensions/vendor_hwprobe.h
- Wrap some long lines
- Link to v8: https://lore.kernel.org/r/20240724-xtheadvector-v8-0-cf043168e137@xxxxxxxxxxxx

Changes in v8:
- Rebase onto palmer's for-next
- Link to v7: https://lore.kernel.org/r/20240724-xtheadvector-v7-0-b741910ada3e@xxxxxxxxxxxx

Changes in v7:
- Add defs for has_xtheadvector_no_alternatives() and has_xtheadvector()
  when vector disabled. (Palmer)
- Link to v6: https://lore.kernel.org/r/20240722-xtheadvector-v6-0-c9af0130fa00@xxxxxxxxxxxx

Changes in v6:
- Fix return type of is_vector_supported()/is_xthead_supported() to be bool
- Link to v5: https://lore.kernel.org/r/20240719-xtheadvector-v5-0-4b485fc7d55f@xxxxxxxxxxxx

Changes in v5:
- Rebase on for-next
- Link to v4: https://lore.kernel.org/r/20240702-xtheadvector-v4-0-2bad6820db11@xxxxxxxxxxxx

Changes in v4:
- Replace inline asm with C (Samuel)
- Rename VCSRs to CSRs (Samuel)
- Replace .insn directives with .4byte directives
- Link to v3: https://lore.kernel.org/r/20240619-xtheadvector-v3-0-bff39eb9668e@xxxxxxxxxxxx

Changes in v3:
- Add back Heiko's signed-off-by (Conor)
- Mark RISCV_HWPROBE_KEY_VENDOR_EXT_THEAD_0 as a bitmask
- Link to v2: https://lore.kernel.org/r/20240610-xtheadvector-v2-0-97a48613ad64@xxxxxxxxxxxx

Changes in v2:
- Removed extraneous references to "riscv,vlenb" (Jess)
- Moved declaration of "thead,vlenb" into cpus.yaml and added
  restriction that it's only applicable to thead cores (Conor)
- Check CONFIG_RISCV_ISA_XTHEADVECTOR instead of CONFIG_RISCV_ISA_V for
  thead,vlenb (Jess)
- Fix naming of hwprobe variables (Evan)
- Link to v1: https://lore.kernel.org/r/20240609-xtheadvector-v1-0-3fe591d7f109@xxxxxxxxxxxx

---
Charlie Jenkins (13):
      dt-bindings: riscv: Add xtheadvector ISA extension description
      dt-bindings: cpus: add a thead vlen register length property
      riscv: dts: allwinner: Add xtheadvector to the D1/D1s devicetree
      riscv: Add thead and xtheadvector as a vendor extension
      riscv: vector: Use vlenb from DT for thead
      riscv: csr: Add CSR encodings for CSR_VXRM/CSR_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
      riscv: Add ghostwrite vulnerability

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  |  19 ++
 .../devicetree/bindings/riscv/extensions.yaml      |  10 +
 arch/riscv/Kconfig.errata                          |  11 +
 arch/riscv/Kconfig.vendor                          |  26 ++
 arch/riscv/boot/dts/allwinner/sun20i-d1s.dtsi      |   3 +-
 arch/riscv/errata/thead/errata.c                   |  28 ++
 arch/riscv/include/asm/bugs.h                      |  22 ++
 arch/riscv/include/asm/cpufeature.h                |   2 +
 arch/riscv/include/asm/csr.h                       |  15 +
 arch/riscv/include/asm/errata_list.h               |   3 +-
 arch/riscv/include/asm/hwprobe.h                   |   3 +-
 arch/riscv/include/asm/switch_to.h                 |   2 +-
 arch/riscv/include/asm/vector.h                    | 225 +++++++++++----
 arch/riscv/include/asm/vendor_extensions/thead.h   |  48 ++++
 .../include/asm/vendor_extensions/thead_hwprobe.h  |  19 ++
 .../include/asm/vendor_extensions/vendor_hwprobe.h |  37 +++
 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/bugs.c                           |  55 ++++
 arch/riscv/kernel/cpufeature.c                     |  58 +++-
 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                    |   5 +
 arch/riscv/kernel/vector.c                         |  24 +-
 arch/riscv/kernel/vendor_extensions.c              |  10 +
 arch/riscv/kernel/vendor_extensions/Makefile       |   2 +
 arch/riscv/kernel/vendor_extensions/thead.c        |  29 ++
 .../riscv/kernel/vendor_extensions/thead_hwprobe.c |  19 ++
 drivers/base/cpu.c                                 |   3 +
 include/linux/cpu.h                                |   1 +
 tools/testing/selftests/riscv/vector/.gitignore    |   3 +-
 tools/testing/selftests/riscv/vector/Makefile      |  17 +-
 .../selftests/riscv/vector/v_exec_initval_nolibc.c |  94 +++++++
 tools/testing/selftests/riscv/vector/v_helpers.c   |  68 +++++
 tools/testing/selftests/riscv/vector/v_helpers.h   |   8 +
 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  | 305 +++++++++++++--------
 42 files changed, 1048 insertions(+), 272 deletions(-)
---
base-commit: 0e3f3649d44bf1b388a7613ade14c29cbdedf075
change-id: 20240530-xtheadvector-833d3d17b423
-- 
- Charlie