[v11,00/14] riscv: Add support for xtheadvector

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@rivosinc.com>

[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].

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@rivosinc.com/
[4] https://lore.kernel.org/lkml/20240719-support_vendor_extensions-v3-4-0af7587bbec0@rivosinc.com/T/

---
Changes in v11:
- Fix an issue where the mitigation was not being properly skipped when
  requested
- Fix vstate_discard issue
- Fix issue when -1 was passed into
  __riscv_isa_vendor_extension_available()
- Remove some artifacts from being placed in the test directory
- Link to v10: https://lore.kernel.org/r/20240911-xtheadvector-v10-0-8d3930091246@rivosinc.com

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@rivosinc.com

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@rivosinc.com

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

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@rivosinc.com

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@rivosinc.com

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

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@rivosinc.com

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@rivosinc.com

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@rivosinc.com

---
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                    | 222 +++++++++++----
 arch/riscv/include/asm/vendor_extensions/thead.h   |  47 ++++
 .../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                           |  60 ++++
 arch/riscv/kernel/cpufeature.c                     |  59 +++-
 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, 1051 insertions(+), 271 deletions(-)
---
base-commit: 0eb512779d642b21ced83778287a0f7a3ca8f2a1
change-id: 20240530-xtheadvector-833d3d17b423