[PATCH v3 0/3] RISC-V: Add Bitmanip/Scalar Crypto HWCAP

Hongren (Zenithal) Zheng
2022-06-12T18:44:28Z

This patchset proposes a currently viable and forward
compatible way to expose the bitmanip/scalar crypto
capability of the platform to the userspace.

Currently viable refers to the property that hardware
platforms can easily modify the riscv,isa field in DT to
tell the kernel it has the capability. Note that QEMU
has already done so in its device tree.

Forward compatible refers to the property that userspace
can still detect the capability of the environment by
using HWCAP regardless of how the mechanism changes
below kernel in the future. I do know that it has not
been settled how to discover a capability, but I think
kernel has to offer some API after all, and HWCAP
is the preferred way among other mechanisms for now.

A note here is that the draft riscv-platform spec
considers DT as mandatory discovery mechanism for embedded platform
For other discovery mechanism like ACPI/SMBIOS, similar
code path can be added but the HWCAP interface could
remain unchanged

More discussion on userspace discovering
can be found on my PR to openssl
https://github.com/openssl/openssl/pull/18197

---
v2:
* Fixed checkpatch problem found by Heiko Stuebner
* rebased on riscv/for-next as that branch has merged
the support of Svpbmt extension
* Changed the order of logical ids in riscv_isa_ext_id
to the order specified in riscv-isa-manual
* added note on riscv-platform-spec

v3:
* rebased on master as riscv/for-next has been merged
* fix commit message as suggested by Conor Dooley

Hongren (Zenithal) Zheng (3):
RISC-V: add Bitmanip/Scalar Crypto parsing from DT
RISC-V: uapi: add HWCAP for Bitmanip/Scalar Crypto
RISC-V: HWCAP: parse Bitmanip/Scalar Crypto HWCAP from DT

arch/riscv/include/asm/elf.h | 2 +
arch/riscv/include/asm/hwcap.h | 22 +++++++-
arch/riscv/include/uapi/asm/hwcap.h | 22 ++++++++
arch/riscv/kernel/cpu.c | 14 +++++
arch/riscv/kernel/cpufeature.c | 81 +++++++++++++++++++++++++----
5 files changed, 129 insertions(+), 12 deletions(-)

--
2.35.1