[PATCH v2 0/3] arm64: Add two HWCAPs for Arm v8.7 FP behaviour
Joey Gouly
joey.gouly at arm.com
Tue Dec 7 04:42:23 PST 2021
This series adds new HWCAPs for two Arm v8.7 features:
- FEAT_AFP: Alternate floating-point behavior for specific
floating point instructions.
- FEAT_RPRES: Increased precision of Reciprocal Estimate and
Reciprocal Square Root Estimate from an 8-bit mantissa to a
12-bit mantissa.
These features can be enabled by userspace by setting some new bits
in FPCR. These new bits are FPCR.{NEP, AH, FIZ}. Since these must be
explicitly enabled by userspace, this should not affect existing
applications.
This has been tested with:
- FVP: combinations of both features, including mismatched CPUs
- qemu: regression test, neither feature is supported
- juno: regression test, neither feature is supported
Changes since v1 [1]:
- Switch WFxT supported bit to the new value in ID_AA64ISAR2_EL1
Thanks,
Joey
Joey Gouly (3):
arm64: cpufeature: add HWCAP for FEAT_AFP
arm64: add ID_AA64ISAR2_EL1 sys register
arm64: cpufeature: add HWCAP for FEAT_RPRES
Documentation/arm64/cpu-feature-registers.rst | 17 +++++++++++++++++
Documentation/arm64/elf_hwcaps.rst | 8 ++++++++
arch/arm64/include/asm/cpu.h | 1 +
arch/arm64/include/asm/hwcap.h | 2 ++
arch/arm64/include/asm/sysreg.h | 11 +++++++++++
arch/arm64/include/uapi/asm/hwcap.h | 2 ++
arch/arm64/kernel/cpufeature.c | 13 +++++++++++++
arch/arm64/kernel/cpuinfo.c | 3 +++
arch/arm64/kvm/sys_regs.c | 2 +-
9 files changed, 58 insertions(+), 1 deletion(-)
--
2.17.1
More information about the linux-arm-kernel
mailing list